Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

An integrated rice panicle phenotyping method based on X-ray and RGB scanning and deep learning

Rice panicle phenotyping is required in rice breeding for high yield and grain quality.To fully evaluate spikelet and kernel traits without threshing and hulling,using X-ray and RGB scanning,we developed an integrated rice panicle phenotyping system and a corresponding image analysis pipeline.We compared five methods of counting spikelets and found that Faster R-CNN achieved high accuracy(R~2 of 0.99)and speed.Faster R-CNN was also applied to indica and japonica classification and achieved 91%accuracy.The proposed integrated panicle phenotyping method offers benefit for rice functional genetics and breeding.

地面激光扫描点云与无人机影像点云融合应用

通过建立高精度的桥梁三维点云模型,检查桥梁病害情况并拟合绘制出桥梁线形。首先以无人机近景摄影、环绕飞行、井字飞行获取某双线特大桥梁主体与细部纹理数据,然后将不同航线采集的数据在Context Capture软件里面进行三维重建,将桥梁主体与细部影像融合生成完整桥梁点云1。运用Trimble SX12仪器完成对桥梁一体化扫描,获得完整桥梁点云2。提出基于双向KD-tree优化的ICP(Iterative Closest Point)算法对无人机航摄桥梁点云1与地面激光扫描桥梁点云数据2进行配准融合,加密后的桥梁点云用于建立运营铁路双线特大桥精细化三维实景建模。提出基于KD-tree的PCA(Principal Component Analysis)算法完整提取出桥梁吊索点云,运用最小二乘法拟合出桥梁拱轴线线形、RANSAC算法拟合出桥面线形。通过与单一无人机、单一地面激光扫描精度及完整性对比分析,以验证融合建模的有效性。研究结果表明:融合建模的模型水平精度1.71 cm、垂直方向精度1.25 cm,较单一无人机建模精度在水平与竖直方向分别提升16.59%与20.89%;融合建模的完整性为98.17%,纹理效果更加真实,并检查出桥墩存在蜂窝麻面、渗水等病害,拱肋存在涂装锈蚀、破裂等病害。该研究可为桥梁三维点云模型应用研究提供思路参考,具有较好的应用前景。

基于机载激光扫描和倾斜影像匹配的点云构建及差异性分析

点云是三维空间数据的重要组成部分,机载激光扫描和倾斜影像匹配是两种主要点云构建技术,具有共性与差异性。本文旨在分析机载激光扫描和倾斜影像匹配技术构建点云的差异性,首先阐述了机载激光扫描和倾斜影像匹配点云构建的具体方法,然后结合案例,从点云构建效果、数据完整性、密度、精度和植被穿透性等方面进行比较和分析。结果表明,两种技术构建点云都具有较好的数据完整性,均能生产高密集点云,远超规范要求,精度相当且较高,但是激光扫描在遮挡区有漏洞,影像匹配局部盲区细节失真;激光点云具有较好的穿透性,能实现不同植被覆盖区域地面点云构建,而影像匹配点穿透性差,在密集植被区域存在缺失甚至不能构建地面点。研究结果为后续点云构建方法的选用和优化提供了参考,具有一定的研究与应用价值。

摆臂式全向移动机器人双模式轨迹跟踪研究

为了提升室外轮式移动机器人全向机动能力,文中提出一种通过普通轮作为驱动的移动机器人,根据不同动力分配及摆腿转角实现四轮转向(4WS)、斜行和原地转向模式。基于斜行及4WS模式设计了双模式混合控制器,其中,斜行模式采用多点预瞄模糊补偿轨迹跟踪控制,4WS模式采用增量线性时变模型预测控制(ILTV-MPC)。通过试验样机的横、纵向跟踪性能试验得到双模式混合控制器所需的约束条件。采用Simulink∕CarSim联合仿真平台对控制器的有效性进行验证。采用混合控制器的移动机器人底盘在低曲率跟踪时较4WS模式均方根误差相差0.18%,且横摆角与横摆角速度维持不变。结果表明:混合控制器保证全轮转向机器人低曲率跟踪精度的同时提升了其横摆稳定性。

基于不同数据采集方式构建城市三维模型相关技术研究

为探索基于不同数据采集方式构建城市三维模型相关技术,本文以具有代表性的建筑物为研究对象,通过对无人机倾斜摄影、地面三维激光扫描、手持三维激光扫描仪等三种设备构建三维模型的技术路线、适用范围、数据采集、精度指标对比等方面进行相关技术研究。

三维激光扫描及倾斜摄影技术在建筑改造前期中的联合应用研究——以黑龙江华电能源股份有限公司综合楼改造方案为例

文章以现代测量工具为载体,以被改造建筑为研究对象,从建筑实际出发,应用现代设备技术手段解决原始图纸缺失及手工测量误差较大的情况。依托高精度的建筑三维内部模型及航空倾斜摄影模型,可绘制建筑内部平面图及实景立面图,从而达到高效方案设计、工程量、概预算准确、施工图纸精准的预期,并且提升后续设计方案施工的可靠性。简单的跨专业整合作业,不仅提升了设计者对项目前期的总体把控,还通过专业的设备及前沿的改造技术方法,获得相关认可及行业影响力。

历史文化资源建档中的测绘新技术应用

以历史文化街区、历史文化名镇名村、历史建筑等为代表的历史文化资源,是城市历史文化传承的重要载体。为更好地保护历史文化遗产,近年来各地广泛开展了历史文化资源保护的相关工作。在重庆市开展的历史文化资源测绘建档工作中,项目组综合运用了三维激光扫描、倾斜摄影等空地一体的非接触式数据采集,以及点云融合、分类、去噪、建模、自动绘图等技术,形成了以二维图形、激光点云、实景三维、精细三维、空地影像和高清照片相结合的测绘成果体系,顺利完成了各类历史文化资源的建档和入库,取得良好效果。

融合激光点云的低空倾斜摄影测量技术在旧城改造中的应用

老旧小区的改造提升是切实关系到民生福祉的重要工程,在旧城改造中高效、精准地采集目标建筑物空间数据对工程造价核算、规划设计等都具有重要意义。常见的三维激光扫描及倾斜摄影测量技术受扫描视角及影像畸变等影响均存在一定局限性。本文将移动式三维激光扫描仪获取的点云数据和低空倾斜摄影测量生成的点云数据进行融合,研究结果表明,本文提出的综合测量法绘制的立面成果图精度提升明显,且效率与传统全站仪法相比具有较高的优越性,对提升旧城改造工程质量具有一定参考价值。

基于多源数据融合的城市建筑物三维可视化研究

针对倾斜摄影测量技术在建筑物模型生成中所存在的盲区、数据缺失和质量不达标等问题,介绍了融合倾斜摄影测量与三维激光扫描技术来构建精细三维模型的方法。采用无人机和三维激光扫描仪作为实验设备,获取到的数据经过配准、去噪、几何建模及纹理映射等处理,并运用ICP算法完成了点云的精细匹配,实现了多源点云数据的融合。与传统的单一建模方法相比,从模型的精度和纹理结构方面全面评估了融合模型的质量。结果显示,融合模型呈现出清晰的纹理和完整的几何结构,模型误差明显低于倾斜摄影模型,且精度接近三维激光扫描模型。该方法最终实现了对城市复杂建筑物的三维模型重建,可为同类项目提供借鉴。

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。

基于无人机倾斜摄影测量技术的复杂重丘区三维重构技术研究

结合无人机倾斜摄影技术和三维激光扫描技术两种方法,分析复杂重丘区地形条件下三维重构技术应用的可实施性,将地面三维激光点云与密集匹配点云配准融合得到完整的复杂重丘区三维点云模型,在生产传统平立剖图件的基础上,以三维点云和实景三维模型的形式对复杂重丘区进行数字化建档,为复杂地形测绘提供了理论支撑和技术参考。

地面激光扫描融合倾斜摄影在拆迁测绘中的应用

随着城市化的高速发展,深圳市面临着建设空间不足的问题愈发严峻,而城市更新成为解决这一问题的重要途径。传统拆迁测绘方法是通过外业入户调查测量房屋及附属物边长及相关数据,内业通过软件测算面积并编制报告,难以在不增加成本的情况下提速增效并满足不断加速推进的城市更新工作。本文提出基于地面三维激光扫描技术融合无人机倾斜摄影测量技术的新型测绘模式,并在深圳市福田区岗厦村城市更新拆迁测绘探索使用。试验结果证明,通过与传统测绘方法比较,基于地面激光扫描及倾斜摄影数据生成海量点云数据、实景三维模型等成果,可以快速生产出建筑物的层型图,建筑物边长尺寸、面积精度都符合规范要求,极大地简化了外业测量工作,能快速满足生产需要。

脊柱旁正中短轴斜扫描超声定位行腰硬联合麻醉在肥胖产妇无痛分娩中的临床应用

目的探讨脊柱旁正中短轴斜扫描超声定位行腰硬联合麻醉在肥胖产妇无痛分娩中的临床应用效果。方法选取60例无痛分娩产妇为研究对象,采用随机数字表法分为两组,各30例。对照组采用传统手触摸体表进行标志定位,研究组采用脊柱旁正中短轴斜扫描进行标记定位,比较两组穿刺成功时间、穿刺次数及并发症发生情况。结果研究组穿刺成功时间短于对照组,穿刺次数少于对照组,差异有统计学意义(P<0.05);研究组并发症发生率为13.33%,低于对照组的46.67%,差异有统计学意义(P<0.05)。结论脊柱旁正中短轴斜扫描超声定位行腰硬联合麻醉应用于肥胖产妇无痛分娩中,能明显缩短穿刺时间,减少穿刺次数,降低并发症发生率,值得推广与应用。

The Study Internal Structure of the Annual Layers in Lake Sediments Using Synchrotron Radiation with X-ray Focusing Optics

1 Introduction Annually laminated(varve)sedimentary deposits are considered as one of the most important archives,since they offer precise temporal information(years)in combination with high time resolutions.Bottom sediments of the lakes contain detailed geochemical information on

An Assessment of Both Patients and Medical Staff Awareness of the Risks of Ionizing Radiation from CT Scan in Cameroon

Objectives: To assess the patients and health personnel’s level of awareness on risks related to ionizing radiation during CT scan. Materials and methods: Three questionnaires were addressed to patients, prescribing physicians, and the medical imaging staff for three hospitals respectively. This permitted us to assess their knowledge on the benefits and risks of the required medical exam, based on the dangers of being exposed to X-rays, especially induced-radiation cancer following the amount of X-rays received during a CT scan and the possibility of not receiving radiation as tools of diagnosis. Results: 150 patients, 84 referring doctors of CT scan tests and 60 medical imaging personnel were retained. For patients, only 7.1% received information on the benefits and risks of their exams, and 34.4% believed that x-rays were harmful to their health. For the prescribers, 46.7% took into account the benefits/risk ratio before prescribing a test and only 16.7% of the referring doctors have informed the patient of the risks related to X-ray. 90% of the medical imaging staff ensures that the required test is justified, and 50% informed the patient on the risks associated with their radiation exposure, and the increased risk of developing cancer. 65% of the imaging staff could not estimate the dose that the patient will receive during the medical test. 25% mentioned the dose received during the acquisition in the patient’s exam report. Conclusion: This study confirms that the referring doctors, the patients, and the radiologists have a low knowledge concerning the risks associated with radiation exposure during a CT scan assessment. We will therefore say that patients and prescribers are not aware of the doses of radiation on CT and their possible risks, even though there is a risk of developing cancer.

Neutron Activation Analysis and Scanning Electron Microscopy of Phytoplankton in the Coastal Zone of Crimea (The Black Sea)

The physiology and ecology of planktonic organisms are influenced by the concentration, chemical speciation and resulting bioavailability of some trace metals. The determination of the elemental structure of phytoplankton is important for interpretation of physiological and functional states of coastal ecosystems. The present study is focused on the structure and elemental composition of the phytoplankton assemblages from the different coastal zones by instrumental neutron activation analysis (INAA), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). For the first time these complementary techniques were simultaneously applied to study the Black Sea phytoplankton. The concentrations of 45 elements in the coastal phytoplankton communities used as bioindicator of inorganic contamination of the Black Sea coastal area near Sevastopol, Ukraine, were determined. Phytoplankton samples were collected by total tows of the plankton net with 35 μm pore size at 3 stations situated in polluted and relatively pristine water areas of the Sevastopol coastal zone during autumn period of the phytoplankton growth. The concentration of Mg, Al, Sc, Ti, V, Mn, As, Rb, Ba, Th and Fe, Cr increases exponentially from relatively pristine station to more polluted station and 10-times and 3-times greater, respectively, in the phytoplankton of the Sevastopol Bay. The rare-earth elements have relatively the same concentration values less than 1 μg/g and tend to accumulate in the phytoplankton from the polluted station in the Sevastopol Bay. The obtained results are in a good agreement with the elemental concentration data in the oceanic plankton, plankton communities from the White Sea and the Black Sea. Using energy-dispersive X-ray spectrometry the mineral particles of unknown origin and impurities of copper (0.42% by weight) in the phytoplankton at the polluted station and zinc (0.57% by weight) at the relatively pristine station were determined.

Mineral Particles Found on the Hairs of Holy Maria-Magdalena Studied by Scanning Electron Microscopy and Elemental Analysis

The presumed hairs of Holy Maria-Magdalena are studied here for mineral particles found on their surfaces, by the techniques of scanning electron microscopy coupled with energy dispersive X-ray. Exploration by these techniques of the hair surfaces allows us to observe and study some marble fragments that can originate from the walls of the sarcophagus in which Maria-Magdalena’s remains were kept. These new findings support the authenticity of the hair as traditionally reported in the French “tradition des Saints de Provence”.

倾斜摄影与激光扫描在土石方测算中的比较研究

随着数字化测量技术的发展,无人机被越来越广泛地应用于工程建设领域,其中倾斜摄影技术、三维激光扫描技术尤其是机载激光雷达逐渐应用于土石方测量工作中,均具有作业速度快、测算精度高、地形适应能力强等特点。但目前研究中,针对两者的工作效率与测算结果的比较研究鲜有涉及。为对2种方法在土石方测算中的应用进行比较,通过实证研究对其应用进行对比分析。结果表明,倾斜摄影与激光扫描作业速度快、精度高;两者相比,倾斜摄影的作业时间仅仅为激光扫描的54.17%,测量精度前者比后者高大约2倍。可见,倾斜摄影与激光扫描在土石方测算中均有显著优势,而倾斜摄影的优势更为突出。

钢渣粉/聚酯纤维沥青混合料水稳定性研究

为了实现钢渣粉在沥青路面中的可持续利用,同时结合河南省冬季冰雪天气下路面的除冰情况,研究了掺有聚酯纤维与钢渣粉沥青混合料的水稳定性。制备4种聚酯纤维掺量(0、0.3%、0.4%、0.5%)AC-13沥青混合料开展复盐(掺量配比为NaCl∶CaCl2∶CH2COONa=1∶1∶2)冻融循环劈裂试验,结果表明聚酯纤维掺量为0.4%时,沥青混合料水稳定最好;在最佳纤维掺量下制备5种替代率(0、25%、50%、75%、100%)钢渣粉沥青混合料,采用冻融劈裂抗拉强度比(freeze-thaw splitting tensile strength ratio,TSR)确定最佳钢渣粉替代率为75%,混合料水稳定性最佳;通过冻融腐蚀因子K评价沥青混合料的抗侵蚀性能,结果表明:聚酯纤维/钢渣粉沥青混合料的抗侵蚀性能最强,聚酯纤维沥青混合料次之,普通石灰岩沥青混合料最弱。通过电镜扫描(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)技术探索钢渣粉/聚酯纤维沥青混合料界面黏附作用的改性机理。微观分析表明:掺量为0.4%的聚酯纤维形成的纤维网状结构以及沥青、钢渣粉(75%的替代率)和矿粉三者存在界面能量作用可以很好地改善沥青混合料的水稳定性。