Experimental Evaluation of CT Number Changes in 320-Row CBCT Volume Scan for Proton Range Calculation

We investigated the longitudinal positional dependence of CT number in 320-row Cone Beam Computed Tomography (CBCT) volume scan (320-row volume scan) using a simple geometric phantom (SGP) and a chest simulation phantom (CSP) in order to evaluate its effect on proton range calculation. The SGP consisted of lung substitute material (LSM) and a cylindrical phantom (CP) made of high-density polyethylene. The CSP was an anthropomorphic phantom similar to the human chest. The two phantoms were scanned using 320-row volume scan in various longitudinal positions from the central beam axis. In experiments using the SGP, an image blur at the boundary of the two materials became gradually evident when the LSM was placed far away from the beam central axis. The image blur of the phantom was consistent with the gradation in CT number. The maximum difference in CT numbers between the 64-row helical scan and 320-row volume scan at the boundary of the two materials was consistent with approximately 50% of the relative proton stopping power. In contrast, the CT number profile in each longitudinal position was fairly consistent and longitudinal positional dependence rarely occurred in the CSP experiments. Pass lengths of CT beams through areas with widely different electron densities were shorter, and thus did not significantly impact CT numbers. Based on findings from the CSP experiments, we considered 320-row volume scan to be feasible for proton range calculation in clinical settings, although the relatively large longitudinal positional dependence of CT number should be accounted for when doing so.

THE RAPID DETERMINATION FOR BENZO(a)PYRENE WITH SYNCHRONOUS FLUORESCENCE SPECTROSCOPY SCANNING IN DEFINED RANGE OF DUAL—WAVELENGTHS

A rapid method of determination of BaP in various environmental samples,using synchronous fluorescence spectroscopy scanning in defined range of dual-wavelengths(SFDW)is described in this paper.

STUDY ON THE SCANNING PROBE MICROSCOPE WITH WIDE MEASURING RANGE

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Mapping tree canopies in urban environments using airborne laser scanning (ALS):a Vancouver case study

Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and modulation of evapotranspiration. It also plays an important role filtering urban water systems and reducing storm water runoff.Methods: We investigate the capacity of ALS data to individually detect, map and characterize large(taller than15 m) trees within the City of Vancouver. Large trees are critical for the function and character of Vancouver’s urban forest. We used an object-based approach for individual tree detection and segmentation to determine tree locations(position of the stem), to delineate the shape of the crowns and to categorize the latter either as coniferous or deciduous.Results: Results indicate a detection rate of 76.6% for trees > 15 m with a positioning error of 2.11 m(stem location). Extracted tree heights possessed a RMSE of 2.60 m and a bias of-1.87 m, whereas crown diameter was derived with a RMSE of 3.85 m and a bias of-2.06 m. Missed trees are principally a result of undetected treetops occurring in dense, overlapping canopies with more accurate detection and delineation of trees in open areas.Conclusion: By identifying key structural trees across Vancouver’s urban forests, we can better understand their role in providing ecosystem goods and services for city residents.

Processing Methods for Conical Scan Hopped-Frequency Signal

The new radar system of combination of the hopped-frequency with the conical scan is presented. According to the principle and expression of the conical scan hopped-frequency signal, the angle processing method in which angle information is obtained by taking discrete Fourier transform （DFT） for the conical envelop of each scattering centre by means of high range resolution profile （HRRP） is presented, and the corresponding formula is derived. The influence of non-ideal factors, such as amplitude fluctuation noise and system noise, leakage of time and frequency domain, unstable rotation of antenna, and missile rotation, on angle-measurement precision and the possible solving methods are also focused on. The simulation results show that the combination of the hopped-frequency and conical scan system could get satisfactory angle information, which could ensure good quality when used in practical tracking radar.

Scan matching using line segment relationships for map-based localization of mobile robot

A new scan matching method for mobile robot localization is presented, which takes line segment as the feature and matches the real scans in the given reference map by relationships of the directional-defined line segments. The alignment was done by hierarchically identifying the multiple relationships and the result was recorded in a correspondence matrix, where the best match is defined and selected for localization. It is indicated that the searching algorithm of the best match can find the ambiguities and get rid of them. This method with less computational cost works well in occluded environment, and can correct the error in pose estimation without the need for the estimation itself. The efficiency, accuracy and robustness of this method were verified by experiments of localization in an occluded environment and a long-distance indoor navigation.

Seamless integration of above-and undercanopy unmanned aerial vehicle laser scanning for forest investigation

Background:Current automated forest investigation is facing a dilemma over how to achieve high tree-and plotlevel completeness while maintaining a high cost and labor efficiency.This study tackles the challenge by exploring a new concept that enables an efficient fusion of aerial and terrestrial perspectives for digitizing and characterizing individual trees in forests through an Unmanned Aerial Vehicle(UAV)that flies above and under canopies in a single operation.The advantage of such concept is that the aerial perspective from the above-canopy UAV and the terrestrial perspective from the under-canopy UAV can be seamlessly integrated in one flight,thus grants the access to simultaneous high completeness,high efficiency,and low cost.Results:In the experiment,an approximately 0.5 ha forest was covered in ca.10 min from takeoff to landing.The GNSS-IMU based positioning supports a geometric accuracy of the produced point cloud that is equivalent to that of the mobile mapping systems,which leads to a 2–4 cm RMSE of the diameter at the breast height estimates,and a 4–7 cm RMSE of the stem curve estimates.Conclusions:Results of the experiment suggested that the integrated flight is capable of combining the high completeness of upper canopies from the above-canopy perspective and the high completeness of stems from the terrestrial perspective.Thus,it is a solution to combine the advantages of the terrestrial static,the mobile,and the above-canopy UAV observations,which is a promising step forward to achieve a fully autonomous in situ forest inventory.Future studies should be aimed to further improve the platform positioning,and to automatize the UAV operation.

3D laser scanning strategy based on cascaded deep neural network

A 3D laser scanning strategy based on cascaded deep neural network is proposed for the scanning system converted from 2D Lidar with a pitching motion device. The strategy is aimed at moving target detection and monitoring. Combining the device characteristics, the strategy first proposes a cascaded deep neural network, which inputs 2D point cloud, color image and pitching angle. The outputs are target distance and speed classification. And the cross-entropy loss function of network is modified by using focal loss and uniform distribution to improve the recognition accuracy. Then a pitching range and speed model are proposed to determine pitching motion parameters. Finally, the adaptive scanning is realized by integral separate speed PID. The experimental results show that the accuracies of the improved network target detection box, distance and speed classification are 90.17%, 96.87% and 96.97%, respectively. The average speed error of the improved PID is 0.4239°/s, and the average strategy execution time is 0.1521 s.The range and speed model can effectively reduce the collection of useless information and the deformation of the target point cloud. Conclusively, the experimental of overall scanning strategy show that it can improve target point cloud integrity and density while ensuring the capture of target.

光学相控阵性能参数仿真分析与实验研究

详细介绍了一维光学相控阵的扫描特性,仿真分析了各参数之间的理论关系。通过各参数与波长之间的关系研究,可知波长调制实现纵向角度控制不会明显改变光学相控阵参数变化,论证在波导上刻蚀光栅,利用光栅的衍射特性可实现二维光学相控阵光束扫描。通过实验,实现了一种256通道光栅二维光学相控阵系统,验证了探测距离大于50 m,测距精度优于5 cm,光束发散角小于0.25°,在1515~1595 nm波长范围内,可实现41.2°×11.9°的二维扫描范围。这些理论分析和实验研究为该领域的科研工作者提供理论指导和技术支持,具有重要的应用价值。

TOMO MVCT在图像引导放射治疗中的应用分析

目的探讨螺旋断层放疗(Tomotherapy)时使用不同兆伏级计算机断层扫描(MVCT)参数对放疗精确度的影响,优化图像引导放疗在临床中的应用。方法选择2023年3月—2024年3月在本院接受螺旋断层放疗的154例患者作为研究对象,随机数表法分为对照组(79例)与实验组(75例)两组。对照组头颈部扫描范围10 cm,胸腹部及盆腔扫描范围20 cm;实验组头颈部扫描范围2 cm,胸腹部及盆腔扫描范围5 cm;所有研究对象每日治疗前进行MVCT扫描,观察两组间摆位误差是否存在差别。结果头颈部肿瘤实验组与对照组摆位误差在所有轴向上均无明显差异,且均值相近。胸腹部肿瘤实验组与对照组摆位误差仅在Y轴方向上有显著差别(P<0.01)。X、Z轴方向误差无显著性差别。盆腔肿瘤实验组与对照组摆位误差在所有轴向上摆位误差均无显著性差别。结论图像引导过程中可以适当减少扫描范围,尤其是头颈部及盆腔对放疗摆位误差没有明显影响,可尽量减少扫描范围。

多源干扰下侧扫声呐图像复原的综合校正研究

为了减少因海洋环境以及侧扫声呐工作机理等干扰所造成的声呐图像畸变,提出多源干扰下侧扫声呐图像复原的综合校正方法。针对辐射图像明暗区域差异明显、轮廓特征模糊等问题,基于双伽马函数和Retinex理论设计辐射均衡化和轮廓清晰化算子,实现了图像辐射校正;针对环境干扰及工作机理所造成的图像水柱区及图像压缩等问题,设计了海底点检测因子并通过获取实际平距实现斜距校正;针对AUV速度波动造成的图像异常拖拽和压缩等问题,基于经纬度设计航行速度,并通过校正比例系数复原图像块来实现速度校正。实验测试结果表明,相较于其它方法,文中综合校正方法不仅使校正图像具有均衡性好、特征轮廓清晰、水柱区基本消除和两舷图像衔接平滑的优点,而且SNR指标平均提升了6.060%、ENT指标平均降低了16.583%、SD指标平均降低了49.904%、ENL指标平均增加了78.347%,有效实现了侧扫声呐图像的复原。

基于双向吸收光谱精准标定的光频扫描干涉绝对测距

本文研究了光频扫描干涉绝对测距的长度基准精准标定方法.利用气体吸收光谱在线标定测距系统中作为长度基准的延时长光纤光程,并提出利用加权线性最小二乘方法解决不同吸收谱峰不确定度的差异.针对吸收光谱标定光纤光程重复精度低的问题,提出了利用双向吸收光谱特征融合的方法提升光纤光程标定精密度.针对吸收谱峰绝对光频准确性不足的问题,提出单一吸收光谱比例系数的标定方法,相较于逐一校准谱峰光频的思路更为简单直接,提升了光纤光程标定准确度.为验证上述方法的有效性,分别进行了重复精度评估实验、比例系数标定实验以及精度比对实验.实验结果表明,标定164 m光纤光程的标准差为10-30μm,在系统温度上升及温度稳定条件下,0-10 m及0-15 m的测量范围内,测距标准差不大于5μm,测距比对残差不大于±4μm,显示了该系统良好的测距性能.

A Review of Wideband Wide-Angle Scanning 2-D Phased Array and Its Applications in Satellite Communication

In this review,research progress on the wideband wide-angle scanning two-dimensional phased arrays is summarized.The importance of the wideband and the wide-angle scanning characteristics for satellite communication is discussed.Issues like grating lobe avoidance,active reflection coefficient suppression and gain fluctuation reduction are emphasized in this review.Besides,techniques to address these issues and methods to realize the wideband wide-angle scanning phased array are reviewed.

面向变压器绕组复合光纤状态监测的BOTDR扫频策略研究

为提高布里渊光时域反射计(BOTDR)在变压器绕组复合光纤状态监测中的准确性,提出了一种BOTDR扫频范围选择策略。该策略通过仿真生成了具有不同信噪比、扫频范围和扫频不对称系数的布里渊谱,并采用伪Voigt模型谱拟合算法来计算布里渊频移;同时,研究了信噪比、扫频范围和扫频不对称系数这3个因素对布里渊频移提取准确性的影响规律。实验结果表明:当扫频范围围绕布里渊频移对称时,误差达到最小;在扫频点数固定的情况下,随着扫频范围的增大,频移误差先减小后增大,当扫频范围比布里渊频移变化幅值大一个线宽时,误差达到最小值。

融合激光点云的无人机近景摄影测量在古建筑实景三维重建中的应用研究

在对古建筑物进行三维空间数据采集时,无人机近景摄影测量可以获取目标物真实的纹理信息和空间及语义信息,但是由于其影像畸变大,受误匹配影响粗差点多,因此模型扭曲、拉花等问题严重,而采用地面三维激光扫描仪虽能获取高精度三维点云数据,但由于扫描视角原因,无法获取建筑物完整的点云数据。本文将地面三维激光扫描仪获取的点云数据和无人机近景摄影测量获取的模型数据进行融合应用,并以某塔型古建筑为应用案例,实验结果表明该方法提高了三维模型的几何结构精度,对古建筑(古文物)数字化保护具有较高的参考价值。

基于线扫描技术的受损一维条码解码识别系统设计

传统一维条码解码系统依赖单一扫描,易因条码受损导致解码失败和识别率下降。为解决此问题,文章设计了基于线扫描技术的解码识别系统。首先,构建了片上扫描存储装置并关联Avalon-DSP接口,实现快速连续扫描;其次,为改进一维条码的点位识别方式,采用多角度、多位置线扫描策略,设计解码功能模块,并结合算法优化,实现准确解码受损条码;最后,接入自适应扫描存储数据库,使得数据的处理更加高效准确。测试结果显示,该系统平均错误识别次数低于12次,错误率低,表现出高针对性和稳定性,而且识别转换灵活,识别效果更优。

多源数据数字化技术在石窟寺保护工作中的应用

石窟寺是我国辉煌灿烂的古代文明的集中体现,加强石窟寺的保护利用意义重大。本文以石泓寺石窟的数字化保护为例,提出利用倾斜航空摄影、近景摄影测量、三维激光扫描等技术获取多源数据,并综合多种技术的优势实现石窟寺三维数字化。首先,基于倾斜航空摄影进行石窟寺外部场景的三维数字化、1:500地形图生产、多角度影像和视频的制作;其次,基于三维激光扫描技术和近景摄影测量技术获取石窟寺内部空间结构以及高清的纹理信息,进行石窟寺内部三维模型、立面正射影像图和立面线描图制作。本文的技术方案实现了石窟寺内外场景的高质量数字化工作,也将为类似的石窟寺保护工作提供可行的解决方案和重要参考。

基于投影点密度的车载激光扫描距离图像分割方法

对车载激光扫描系统获取的距离图像的分割进行研究,提出利用投影点密度进行距离图像分割的方法。该方法不需要其他辅助数据就可以进行距离图像的分割,给出应用实例。图像的分割是目标识别、定位、特征提取与建模的基础和关键。距离图像是离散坐标点阵列,不表达目标边界特征和拓扑关系,到目前为止还没有距离图像分割的成熟、可行方法。本文研究成果,展现了激光扫描技术在数据获取、处理研究上的新方向。

地面三维激光扫描仪的检校与精度评估

三维激光扫描技术是一种先进的全自动高精度立体扫描技术。其中,激光扫描测量仪器的精度对工程应用的影响以及对三维点云模型的建立和精度影响至关重要。本文分析了激光扫描仪的主要误差来源,同时介绍了三维激光扫描仪的检校原理和方法,并以Leica公司的HDS3000为例,从测距、测角、大气影响等方面,对激光扫描仪的精度进行测试和评定。

采用红外扫描激光与超声技术的室内空间定位

为了解决当前定位方法无法兼顾高精度、高集成度、多任务性、实时性测量的问题,提出了一种基于激光测距原理的室内空间定位系统。该方法通过单台测量基站向被测空间内发射旋转扫描红外激光信号以及超声脉冲信号,采用旋转扫描红外激光形成多平面约束,采用高精度超声测距形成距离约束。然后,将多平面约束与距离约束相耦合,得到测量靶标的非线性约束方程组。最后,利用非线性最优化算法解算得到测量靶标的精确空间坐标。该方法仅采用单台测量基站即可完成全周向、多任务实时性的空间测量与定位。采用激光跟踪仪系统作为比对基准验证了本方法的测量精度及可靠性。结果显示,在5m的被测空间内,其定位测量误差在0.3mm以内,可满足大多数工业测量应用场合需求。与传统的室内定位方法相比,本方法极大地提高了测量系统的集成度以及测量效率,为全站式空间定位方法提供了新的思路。