空间失稳目标线阵成像畸变分析与三维重建

针对线阵扫描型激光雷达在非合作失稳航天器三维模型重建过程中,存在运动目标线扫数据畸变且目标因失稳导致运动特性难以准确估计问题,提出一种带畸变自修正式三维重建方法,并进行畸变容忍度临界值分析。该方法基于测量系统的角精度与测距精度设计畸变容忍度临界值判定条件,首先根据实际工况与判定条件进行比对,判定是否对线扫数据进行初始畸变恢复;其次,对相邻扫描带畸变点云依次进行配准获取目标运动增量、解算目标瞬时运动参数;然后对目标运动参数进行自修正式处理,去除特征突变点干扰;同时依次恢复点云到初始几何位置,完成初始目标三维重建;最后,通过系统进一步迭代,位姿增量自收敛直至最终满足重建精度要求。仿真结果表明,该方法在缺失非合作目标先验信息的情况下,能够有效避免因线扫描导致的畸变问题,并较为快速地实现满足精度要求的目标三维重建,有较强的鲁棒性。

乌鲁木齐市汉族中学生错畸形调查

目的 了解乌鲁木齐市汉族中学生错牙合畸形患病情况 ,分析常见错牙合畸形患病规律。方法 随机抽取 562名 1 1～ 1 9岁汉族青少年按Angle及毛燮均分类法进行分类 ,以个别正常 牙合和错牙合分类为标准。结果 错牙合畸形患病率男生为 73 .82 % ,女生为 65 .51 % ,两者差异有显著性 (P <0 .0 5)。常见的错牙合畸形为拥挤、深覆盖、个别牙错位 ,患病率分别为 2 0 .46 %、1 6 .38%、9.0 7%。错牙合患者中安格分类以一类最多 (61 .1 3 % ) ,四类最少 (0 .77% )。有正畸治疗史者少见。结论 乌鲁木齐市汉族青少年错牙合畸形者较多 ,应尽快早期防治并增强患者正畸意识。

Correction of seabed layer thickness in processing subbottom profile data

The subbottom profiling is an important means of marine engineering survey, hazardous geology study and continental shelf scientific research. The accuracy of subbottom profile data interpretation has a direct impact on the research and investigation results. Because some of profilers’ transducer and hydrophone are separately installed, when the survey area is very shallow, distortion of shallow layers will be caused if it is seen as a self-excited and self-collected single-channel seismic system. According to the principle of subbottom profiler, the distortion correction formula is deduced and analyzed, providing actual value to using C-View software to interpret such subbottom profile data more accurately. In addition, the seabed sediments sound velocity is one of the key parameters when acquiring and processing the subbottom profile data. On the basis of comparing some sound velocity forecasting empirical equations, the LU Bo’s equation was considered the most appropriate to predict the seabed sediments, sound velocity at near-shore of China. In a survey of an artificial island site, the LU Bo’s equation and the porosity data obtained from geological drilling were utilized to predict the sediments sound velocity, and the sound velocity structure profile was plotted, which was applied in processing the subbottom profile data of the artificial island investigation. The method of using porosity data to predict sediments sound velocity in processing subbottom profile data can improve the interpretation accuracy and it’s of practical significance.

Cascade Kalman filter for gravity anomaly distortion correction based on second order potential model

Using a gravity anomaly covariance function based on the second-order Ganssian Markov gravity anomaly potential model, the state equation of a gravity anomaly signal is obtained in marine gravimetry. Combined with the system state equation and the measurement equation, a new method of the cascade Kalman filter is proposed and applied to the correction of gravity anomaly distortion. In the signal processing procedure, an inverse Kalman filter is used to restore the gravity anomaly signal and high frequency noises first. Then an adaptive Kalman filter, which uses the gravity anomaly state equation as the system equation, is set to estimate the actual gravity anomaly data. Emulations and experiments indicate that both the cascade Kalman filter method and the single inverse Kalman filter method are effective in alleviating the distortion of the gravity anomaly signal, but the performance of the cascade Kalman filter method is better than that of the single inverse Kalman filter method.

X-ray image distortion correction based on SVR

X-ray image has been widely used in many fields such as medical diagnosis,industrial inspection,and so on.Unfortunately,due to the physical characteristics of X-ray and imaging system,distortion of the projected image will happen,which restrict the application of X-ray image,especially in high accuracy fields.Distortion correction can be performed using algorithms that can be classified as global or local according to the method used,both having specific advantages and disadvantages.In this paper,a new global method based on support vector regression（SVR）machine for distortion correction is proposed.In order to test the presented method,a calibration phantom is specially designed for this purpose.A comparison of the proposed method with the traditional global distortion correction techniques is performed.The experimental results show that the proposed correction method performs better than the traditional global one.

Straight line feature based image distortion correction

An image distortion correction method is proposed, which uses the straight line features. Many parallel lines of different direction from different images were extracted, and then were used to optimize the distortion parameters by nonlinear least square. The thought of step by step was added when the optimization method working. 3D world coordination is not need to know, and the method is easy to implement. The experiment result shows its high accuracy.

基于纽玛克法的变截面波形钢腹板组合箱梁畸变效应分析

为研究变截面波形钢腹板组合箱梁(CBGCSWs)在偏心荷载作用下的畸变效应,忽略波形钢腹板的纵向抗弯刚度,通过建立其微段单元平面内、外力系平衡方程,推导了以畸变角为未知量的畸变微分方程,并采用基于共轭梁理论的纽玛克法进行求解,由此建立了偏心荷载作用下变截面CBGCSWs畸变正应力计算理论。以某大跨变截面CBGCSWs桥为工程背景,运用该理论获得了4种不同工况下组合箱梁角点处畸变正应力理论解,并采用空间有限元方法进行了验证,数值解与理论解吻合良好,表明推导的变截面CBGCSWs畸变计算理论正确且精度足够,可供工程参考。在此基础上,比较了变截面CBGCSWs与对应PC箱梁的抗畸变能力,并探讨了横隔板间距、高跨比、宽跨比及钢腹板形状等因素对变截面CBGCSWs畸变正应力的影响规律。结果表明:用波形钢腹板替代混凝土腹板会较大程度削弱箱梁的抗畸变能力,应当引起足够重视;横隔板间距及宽跨比等参数对畸变正应力影响较大,而高跨比及钢腹板形状等则影响很小。

Er,Zr共掺杂对(K0.16Na0.84)0.5Bi4.5Ti4O15压电陶瓷电学和上转换发光性能的影响

采用固相法制备Er、Zr共掺铋层状结构陶瓷(K0.16Na0.84Bi)0.47Er0.02Bi4Ti4–xZrxO15(KNBET–Zr–x,0≤x≤0.12,x为摩尔分数),研究了不同Zr含量对样品的结构、电学与上转换发光性能的影响。结果表明:所有样品均为单一的正交相铋层状结构,无其他杂相出现。随着Zr掺入量的增加,晶格常数a、b、c不断增大,正交畸变(b/a)的值逐渐减小;适量Zr掺杂使样品的介电损耗降低,剩余极化强度2Pr和压电常数d33得到提高;当x=0.04时,样品具有最佳的综合电学性能:介电损耗tanδ=0.61%、压电性能d33=24 p/CN、剩余极化强度2Pr=3.02μC/cm2。在980 nm近红外光源激发下,所有样品均呈现出较强的绿光发射,对应于2H11/2→4I15/2和4S3/2→4I15/2的跃迁。随着Zr离子掺入量增加,正交畸变(b/a)减少,荧光强度逐渐下降。