Impact Point Prediction and Lateral Correction Analysis of Two-dimensional Trajectory Correction Projectiles

Compared with the one-dimensional trajectory correction technology which adjusts longitudinal range, not only does the two-dimensional trajectory correction technology adjust the force in velocity direction, but also need to modulate the lateral force or trajectory (perpendicular to the vertical plane of fire direction). Therefore, the structure of control cabin of two-dimensional trajectory correction projectile (TDTCP) is more complicated than that of one-dimensional trajectory correction projectile (ODTCP). To simplify the structure of control cabin of TDTCP and reduce the cost, a scheme of adding a damping disk to the control cabin of ODTCP has been developed recently. The damping disk is unfolded at the right moment during its flight to change the ballistic drift of spin stabilized projectile. For this technical scheme of TDTCP, a fast and accurate impact point prediction method based on extended Kalman filter is presented. An approximate formula for predicting the ballistic drift and trajectory correction quantity is deduced. And the lateral correction capability for different fire angles and its influencing factors are analyzed. All the work is valuable for further research.

Correction to“Downregulation of FoxM1 inhibits the viability and invasion of gallbladder carcinoma cells,partially dependent on the induction of cellular senescence”

We corrected the mistake of Figure 3,and replaced the incorrect images with the correct ones.The“adenovirus”was a typographical error in writing,and should be revised to“lentivirus”.

Error Correction in the Classroom

Making errors is inevitable in learning a second language.This paper discusses the following questions concerning errors correction in the classroom:Whether to correct errors,what time to correct errors,who corrects errors and how to correct errors respectively.

Optimal combination of the correction model and parameters for the precision geometric correction of UAV hyperspectral images

Nowadays,with the rapid development of quantitative remote sensing represented by high-resolution UAV hyperspectral remote sensing observation technology,people have put forward higher requirements for the rapid preprocessing and geometric correction accuracy of hyperspectral images.The optimal geometric correction model and parameter combination of UAV hyperspectral images need to be determined to reduce unnecessary waste of time in the preprocessing and provide high-precision data support for the application of UAV hyperspectral images.In this study,the geometric correction accuracy under various geometric correction models(including affine transformation model,local triangulation model,polynomial model,direct linear transformation model,and rational function model)and resampling methods(including nearest neighbor resampling method,bilinear interpolation resampling method,and cubic convolution resampling method)were analyzed.Furthermore,the distribution,number,and accuracy of control points were analyzed based on the control variable method,and precise ground control points(GCPs)were analyzed.The results showed that the average geometric positioning error of UAV hyperspectral images(at 80 m altitude AGL)without geometric correction was as high as 3.4041 m(about 65 pixels).The optimal geometric correction model and parameter combination of the UAV hyperspectral image(at 80 m altitude AGL)used a local triangulation model,adopted a bilinear interpolation resampling method,and selected 12 edgemiddle distributed GCPs.The correction accuracy could reach 0.0493 m(less than one pixel).This study provides a reference for the geometric correction of UAV hyperspectral images.

Thermal Fission Rate Calculated Numerically by Particles Multi-passing over SaddlePoint

Langevin simulation of the particles multi-passing over the saddle point is proposed to calculate thermal fission rate.Due to finite friction and the corresponding thermal flutuation,a backstreaming exists in the process of the particle descent from the saddle to the scissio.This leads to that the diffusion behind the saddle point has influence upon the stationary flow across the saddle point.A dynamical correction factor,as a ratio of the flows of multi-and firstoverpassing the saddle point,is evaluated analytically.The results show that the fission rate calculated by the particles multi-passing over the saddle point is lower than the one calculated by the particle firstly passing over the saddle point,and the fomer approaches the results at the scission point.

Performance analysis of real-time and post-mission kinematic precise point positioning in marine environments

This article focuses on the performance analysis of both real-time and post-mission kinematic precise point positioning(PPP)in challenging marine environments.For this purpose,a real dynamic experiment lasting 6 h was carried out on a lake dam in?orum City of Turkey.While the kinematic test was continuing,the real-time PPP coordinates were obtained for each measurement epoch with a commercial real-time PPP(RT-PPP)service,namely the Trimble Center Point RTX.Then the post-mission PPP(PM-PPP)coordinates were calculated by using Multi-GNSS data and the Multi-GNSS Experiment(MGEX)precise products.The kinematic RT-PPP and PM-PPP results showed that the PPP coordinates were consistent with the relative solution at centimetre and decimetre level in horizontal and height components,respectively.This study implies that PPP technique is a powerful tool for highly accurate positioning in both real-time and post-mission modes,even for dynamic applications in harsh environments.

A Stylistic Analysis of an Excerpt from The Corrections

This article focuses on analyzing the excerpt from The Corrections written by Jonathan Franzen.The analysis shed light on the participating characters(Chip and his father,Alfred)by exploring the point of view of the author and on the peculiarities of their family relationship as well as the emotional change of Chip.

Motion modeling and formation form analysis of spacecraft near collinear libration points

To meet the increasing research demand for deep space exploration,especially for the second libration point (L2) conditional periodic orbit (Halo orbit) in the Sun-Earth system,the methods to get analytical Halo orbit and differential-correction Halo orbit were described firstly,and the corresponding orbits accuracy was analyzed.Then,based on the results of third-order and differential-correction Halo orbits,the formation form was studied.Analysis was carried out to discuss the influence of system amplitude,initial phase,and phase difference on the formation form,as well as that of initial orbit values on form accuracy.Finally,some simulation results demonstrate the validity of the proposed methods.

Base-out恢复点为目标手术量的急性共同性内斜视治疗效果分析

目的:探讨Base-out恢复点为目标手术量的急性共同性内斜视(AACE)治疗效果。方法:收治60例AACE患者,对患者进行Base-out恢复点为目标手术量的治疗干预。对比手术效果、Base-out恢复点参数、立体视觉恢复及影响因素。结果:术后左眼、右眼近视屈光度高于术前,术后近距、远距斜视度低于术前(P<0.05)。术后Base-out恢复点近距、远距均低于术前,术后的BI恢复点包括近距、远距高于术前(P<0.05)。结论:AACE患者采用基于Base-out恢复点为目标手术量有较好的治疗效果,改善立体视觉功能。

无缝钢管张力减径工艺减径率分配修正模型理论研究

无缝钢管张力减径工艺减径率分配是孔型分配合理与否的关键步骤,但其分配仍依赖于经验公式。从金属流动的角度分析了减径率的分配规律,在经验的基础上提出了“三点两段统合式”减径率分配修正模型。将修正模型得到的结果与传统模型计算结果以及企业生产数据相比,发现变化趋势相近,减径率和减径量变化曲线更加光滑,应用于生产有利于金属流动。

基于几何约束的倾斜影像特征匹配方法

针对倾斜影像视角变换较大、重复纹理导致匹配数量少、匹配精度不高的问题,提出一种适用于倾斜影像的特征点、线分级匹配方法.首先,用直线提取(检测)算法(LSD)获取影像直线特征,并将直线特征以一定约束进行直线组对,构建直线对区域与改进的SIFT(scale-invariant feature transform)特征描述符进行匹配,使用RANSAC算法剔除误匹配,获得初始匹配结果后再进行核线约束;然后,利用已获得直线对区域进行影像局部纠正,在纠正后的局部影像上采用SIFT匹配并反算回原始影像,利用得到的同名点全局纠正倾斜影像,并进行特征点匹配与采用基于方格的运动统计算法(GMS)剔除误匹配,仍将匹配结果反算回原始影像上;最后,将仿射尺度不变特征变化结果与点拓展匹配结果进行合并,得到最终匹配结果.试验结果表明:本文方法匹配正确率与经典的仿射不变匹算法(ASIFT)的正确率相差不大,但匹配数量却是ASIFT算法的1倍~3倍.

改进Mask RCNN的盾构隧道渗漏水检测方法

渗漏水是盾构隧道结构存在潜在损伤或缺陷的重要表征,快速、准确检测出渗漏水位置,对隧道安全运营和维护具有重要意义。现有的方法大多采用光学影像对隧道渗漏水进行检测,受隧道内空间和光线条件限制,难以获得高质量病害图片。因此,本文提出了一种基于激光点云数据与改进Mask RCNN相结合的渗漏水检测方法。首先对激光点云反射强度进行修正;然后生成灰度图像并建立渗漏水病害数据集;最后在Mask RCNN算法中引入空洞卷积和变形卷积,实现了隧道渗漏水病害的快速检测。利用某地铁采集的数据进行验证,结果表明,本文提出的改进Mask RCNN算法相较于原始算法和FCN算法检测精度均有明显提升,在盾构隧道渗漏水识别方面性能表现较好。

Galileo高精度定位服务初始服务性能评估

从服务改正数可用性、轨道钟差精度等方面综合分析高精度定位服务(high accuracy service,HAS)的性能,同时利用全球各区域的多模GNSS实验跟踪网(multi-GNSS experiment,MGEX)测站分析HAS PPP的性能。结果表明,大部分卫星改正数的可用性在80%以上;GPS和Galileo的空间信号测距误差(signal-in-space ranging error,SISRE)分别为0.163 m、0.097 m;MGEX测站水平方向定位精度均小于0.2 m,垂直方向均小于0.4 m。

一测多评法同时测定桑叶中9种绿原酸类和黄酮类成分

目的:建立一测多评法同时测定桑叶中新绿原酸、绿原酸、隐绿原酸、芦丁、异槲皮苷、异绿原酸B、紫云英苷、异绿原酸A和异绿原酸C的含量。方法:采用Agilent TC-C18色谱柱(250 mm×4.6 mm,5μm),以乙腈(A)-0.1%磷酸水溶液(B)为流动相,梯度洗脱,流速1.0 mL/min,检测波长260、320 nm,柱温30℃。以绿原酸为内参物,分别采用外标法和一测多评(多点校正、斜率校正和单点校正)测定桑叶中9个成分的含量并比较4种方法之间的差异,另外采用多点校正和两点校正法进行色谱峰定位,验证该方法的准确性和可行性。结果:新绿原酸、隐绿原酸、芦丁、异槲皮苷、异绿原酸B、紫云英苷、异绿原酸A和异绿原酸C相对于绿原酸的校正因子分别为0.9072、0.8736、0.6207、0.8547、1.1936、0.5501、1.4369和1.2244(多点校正),且在不同条件下相对校正因子耐用性(RSD<1.5%)和重现性(RSD<5%)良好。外标法和一测多评(多点校正、斜率校正和单点校正)测得桑叶中9个成分含量的结果之间无差异(RSD<1.5%)。相较于相对保留时间,多点校正和两点校正可改善色谱峰的准确定位(相对误差|RE|<3%)。结论:建立了桑叶中9种成分的一测多评法,该法准确可行,可用于桑叶的质量控制。

基于谱分析的红外成像模糊去除算法研究

针对红外成像中出现的像差和运动模糊问题,提出了一种基于谱分析的红外成像模糊去除算法。该方法通过对模糊问题的分析,利用红外图像频谱信息构建了模糊函数估计方法,通过数据拟合项和正则项的优化,实现红外图像的模糊去除。实验在运动模糊图像数据集和静态像差图像上进行测试,结果表明:在数据集模糊去除实验上,相比之前的方法,本文方法峰值信噪比(PSNR,peak signal-to-noise ratio)提升了2.01 dB,结果相似性(SSIM,structural similarity index)提升了0.06;静态像差图像在实验室条件下通过短波红外探测器采集,算法在主观上有较明显的复原效果,且针对高通量光学系统成像复原效果更为显著。

南极光学天文望远镜控制软件关键技术

南极天文望远镜控制软件是望远镜软件系统的重要组成部分,是控制计算机在望远镜用户层和设备层之间运行的关键技术。对于用户层,控制软件需具备全自动观测的交互接口、卫星通信条件下的远程访问和故障诊断等功能;对于设备层,控制软件不但要完成对天体目标的精确指向和精密跟踪、计算并补偿系统误差和控制关键部件以达到目标像质,而且需实现对电源分配系统、除霜及加热系统的控制、设备及环境信息的采集和监测等。相比于普通台址,在南极大陆运行的光学天文望远镜有其独特的特点,控制软件需进行特殊设计。本文重点从操作系统选择、远程建立望远镜指向误差修正模型方法、全自动观测软件接口、卫星通信及远程运维、望远镜实时状态监测和故障诊断等方面探讨了南极天文光学望远镜控制软件的关键技术和设计原则,并展望未来技术的发展,为南极天文望远镜的研制和控制系统研发提供技术储备。

ICESat-2水深提取方法及其反演应用

相比于传统水深测量方法,结合主动激光卫星ICESat-2数据与被动光学遥感影像的主被动融合水深反演方法具有低成本、覆盖面积广、不受地域限制、无需地面实测数据等优点.研究选取澳大利亚大堡礁中部的John Brewer Reef和南部的Fitzroy Reef为实验区,开展主被动融合水深反演实验.针对ICESat-2光子点群信噪比低、光子点水深信息提取和改正难的问题,本文提出基于光子点群高斯分布特征的海面光子点群提取方法和基于深度自适应DBSCAN的海底光子点群提取方法,并顾及海面倾斜引起的入射角偏移,改进了Parrish水体折射改正几何模型.实验表明,基于光子点群高斯分布特征的海面光子点群提取方法和基于深度自适应DBSCAN的海底光子点群提取方法可以高效准确地提取出有效的海面、海底光子点群;经过地球物理改正和基于改进模型的水体折射改正后,水深变浅,且改正项与改正前水深呈线性关系,线性系数约为-0.2550.实验将提取并改正后的ICESat-2光子点水深与经大气校正、耀斑校正、空间域滤波等预处理后的Sentinel-2影像进行空间匹配构建水深反演样本集,并利用单波段模型(SB)、比值模型(BR)、Lyzenga多项式模型(LP)、二次多项式模型(QP)、三次多项式模型(CP)、支持向量回归模型(SVR)、多层感知器模型(MLP)、随机森林回归模型(RF)等水深反演模型对实验区全域水深进行反演.通过对比分析多种水深反演模型在不同地理区域和ICESat-2水深样本分布条件下的表现,研究为不同场景下的主被动融合水深反演策略提供了一定的科学依据.

一种动态双模态线阵相机的联合标定方法

在实际工业应用中,线阵相机在被测物体运动速度快、拍摄视场范围广以及精度要求高的场景下比面阵相机更具优势,并且将二维图像数据与三维点云数据相结合能使信息量更丰富,能更好地还原真实场景。为提高在工业应用场景下的双模态数据的结合精度,提出一种动态双模态线阵相机的联合标定方法,该方法能实现简便快捷的2D线扫相机与3D线扫相机之间的联合标定。实验结果表明,该算法能以较小计算量实现高精度双模态双线扫相机的联合标定。

基于最大图像熵Gamma校正估计的图像特征点检测和匹配方法

提出一种基于最大图像熵Gamma校正估计的图像特征点检测和匹配方法。通过预处理算法来增强图像的对比度,将其应用于图像特征点的检测和匹配。在预处理阶段,首先采用对数函数对图像进行归一化,根据设定的阈值将图像分为明亮和黑暗分量;然后分别对两个分量自适应地选择不同的参数进行Gamma校正,并且确定使其熵最大化的校正参数为每个分量的最佳参数;最后将上述参数应用于Gamma校正生成对应原始图像明亮和黑暗区域的矫正图,并进行融合生成增强的图像。对预处理完的图像进行特征点检测和匹配实验。研究结果表明:所提出的算法相较于未处理算法、HE和自适应Gamma算法,特征点检测后的匹配数量在欠曝光图像上分别提升85.7%、26.4%和15.2%,在过曝光图像上分别提升59.4%、12.2%和103.8%。匹配效果也有较明显提升。