Resolution of Digitized Conjugate Tooth-Face Surface Based on the Theory of Digitized Conjugate Surfaces

According to the principle of meshing engagement and the theory of the digitized conjugate surface, this paper applies the software Conjugater-1.0 that is developed by ourselves to compute, respectively, the digitized conjugate curved surfaces of the straight-tooth surface and drum-tooth surface, which will establish the theoretical and technical foundation for digitized engaging analysis, simulation, and digitized manufacturing technology of the diversified gears.

A Method for Identification and Compensation of Machining Errors of Digital Gear Tooth Surfaces

In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are analyzed directly from the real tooth surfaces.The topography data of the part are off-line measured in the post-process.A comparison is made between two models:CAD model of DGTS and virtual model of the physical measured surface.And a matching rule is given to determine these two surfaces in an appropriate fashion.The developed error estimation model creates a point-to-point map of the real surface to the theoretical surface in the normal direction.A“pre-calibration error compensation”strategy is presented.Through processing the results of the first trail cutting,the total compensation error is predicted and an imaginary digital tooth surface is reconstructed. The machining errors in the final manufactured surfaces are minimized by generating this imaginary surface.An example of ma- chining 2-D DGTS verifies the developed method.The research is of important theoretical and practical value to manufacture the DGTS and other digital conjugate surfaces.

Theory of Digitized Conjugate Surface and Solution to Conjugate Surface

In order to meet the needs of designing and processing digitized surfaces, the method to spreading digitized surface has been proposed. The key technique is to solve the problem of digitized conjugate surface. In the paper, the digitized conjugate surface was theoretically investigated, and the solution of conjugate surface based on digitized surface was also studied. The digitized conjugate surface theory was then proposed, and applied to build the model of solving conjugate surface based on digitized surface. A corresponding algorithm was developed. This paper applies the software Conjugater-1.0 that is developed by ourselves to compute the digitized conjugate surfaces of the drum-tooth surface. This study provides theoretical and technical bases for analyzing engagement of digitized surface, simulation and numerical processing technique. Key words digitized conjugate surface - generating method - simulation CLC number O 186.1 - TH 122 Foundation item: Supported by the National Natural Science Foundation of China (50075031)Biography: Xiao Lai-yuan (1957-), male, Professor, Ph. D candidate, research direction: machanical design & theory, digital technology

A new GIS-compatible methodology for visibility analysis in digital surface models of earth sites

As a GIS tool,visibility analysis is used in many areas to evaluate both visible and non-visible places.Visibility analysis builds on a digital surface model describing the terrain morphology,including the position and shapes of all objects that can sometimes act as visibility barriers.However,some barriers,for example vegetation,may be permeable to a certain degree.Despite extensive research and use of visibility analysis in different areas,standard GIS tools do not take permeability into account.This article presents a new method to calculate visibility through partly permeable obstacles.The method is based on a quasi-Monte Carlo simulation with 100 iterations of visibility calculation.Each iteration result represents 1%of vegetation permeability,which can thus range from 1%to 100%visibility behind vegetation obstacles.The main advantage of the method is greater accuracy of visibility results and easy implementation on any GIS software.The incorporation of the proposed method in GIS software would facilitate work in many fields,such as architecture,archaeology,radio communication,and the military.

A TECHNIQUE OF DIGITAL SURFACE MODEL GENERATION

It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.

An Adaptive and Image-guided Fusion for Stereo Satellite Image Derived Digital Surface Models

The accuracy of Digital Surface Models(DSMs)generated using stereo matching methods varies due to the varying acquisition conditions and configuration parameters of stereo images.It has been a good practice to fuse these DSMs generated from various stereo pairs to achieve enhanced,in which multiple DSMs are combined through computational approaches into a single,more accurate,and complete DSM.However,accurately characterizing detailed objects and their boundaries still present a challenge since most boundary-ware fusion methods still struggle to achieve sharpened depth discontinuities due to the averaging effects of different DSMs.Therefore,we propose a simple and efficient adaptive image-guided DSM fusion method that applies k-means clustering on small patches of the orthophoto to guide the pixel-level fusion adapted to the most consistent and relevant elevation points.The experiment results show that our proposed method has outperformed comparing methods in accuracy and the ability to preserve sharpened depth edges.

Using UAVs for detection of trees from digital surface models

A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.

Study on the Digital Manufacturing System of Ship Model Surface

Because a ship model surface (SMS) is a large double-curved 3-D surface,the machining efficiency of the cur- rent handcraft manufacturing method are very low,and the precision is difficult to control also.In order to greatly improve the machining efficiency and precision of SMS,based on the CAD/CAM/CNC technology,this paper proposed a model of SMS digi- tal manufacturing system,which is composed of five functional modules (preprocess module,CAD module,CAM module,post- process module and CNC module),and a twin-skeg SMS as an example,the key technologies & design principle of the nodtules were investigated also Based on the above research works,the first set of 4-axis SMS Digital Manufacturing System in China has been successfully developed,which can reduce the machining time of the twin-skeg SMS from 30 working days needed for the cur- rent handcrafting manufacturing method to 8 hours now,and which can control more effectively the precision of SMS also.

Primary safe criterion of earth-brushing flight for flying vehicle over digital surface model

In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classification and scale analysis of an isolated obstacle threatening flight safety of terrain-following guidance are made. When the interval of vertical-and cross-sections on DSM is 12. 5 m, the proportion of isolated obstacles to the data amount of DSM model to be loaded is optimal. The main factors influencing the lowest flying height in terrain-following guidance are analyzed, and a primary safe criterion of the lowest flying height over DSM model is proposed. According to their test errors, the lowest flying height over 1:10 000 DSM model can reach 40. 5 m^45. 0 m in terrain-following guidance. It is shown from the simulation results of a typical urban district that the proposed models and methods are reasonable and feasible.

Evaluating the Impacts of Using Different Digital Surface Models to Estimate Forest Height with TanDEM-X Interferometric Coherence Data

In our previous studies, we demonstrated the usefulness of TanDEM-X interferometric bistatic mode with single polarization to obtain forest heights for the purposes of large area mapping. A key feature of our approach has been the use of a simplified Random Volume Over Ground(RVOG) model that locally estimates forest height. The model takes TanDEM-X interferometric coherence amplitude as an input and uses an external Digital Surface Model(DSM) to account for local slope variations due to terrain topography in order to achieve accurate forest height estimation. The selection of DSM for use as a local slope reference is essential, as an inaccurate DSM will result in less accurate terrain-correction and forest height estimation. In this paper, we assessed TanDEM-X height estimates associated with scale variations in different DSMs used in the model over a remote sensing supersite in Petawawa, Canada. The DSMs used for assessments and comparisons included ASTER GDEM, ALOS GDSM, airborne DRAPE DSM, Canadian DSM and TanDEM-X DSM. Airborne Laser Scanning(ALS) data were used as reference for terrain slope and forest height comparisons. The results showed that, with the exception of the ASTER GDEM, all DSMs were sufficiently accurate for the simplified RVOG model to provide a satisfactory estimate of stand-level forest height. When compared to the ALS 95th height percentile, the modeled forest heights had R2 values greater than 80% and Root-Mean-Square Errors(RMSE)less than 2 m. For a close similarity in slope estimation with the ALS reference, coverage across Canada and open data access, the 0.75 arc-second(20 m) resolution Canadian DSM was selected as a preferred choice for the simplified RVOG model to provide TanDEM-X height estimation in Canada.

基于DSM的城市公园对PM_(2.5)和PM_(10)的消减特征研究——以南昌市人民公园为例

【目的】PM_(2.5)、PM_(10)等空气颗粒物是城市空气首要污染物,在城市空气污染中占主导地位。了解固定外源下PM_(2.5)、PM_(10)在城市绿地的消减特征,可为城市阻控空气颗粒物、缓解空气污染提供有利依据。然而目前空气颗粒物的研究大多以点测定方式量化空间结构及植被类型对空气颗粒物的影响,对固定外源污染下PM_(2.5)、PM_(10)在城市绿地空间尺度上的影响机制研究较少。【方法】研究结合DSM与地统计学,以南昌市人民公园为例,探索城市公园阻隔外源污染的空间梯度效应及空间结构类型差异。利用克里金插值法对其空间分布特征进行可视化模拟;利用Arcgis和R语言等软件分析不同空间结构PM_(2.5)、PM_(10)的浓度差异。【结果】人民公园PM_(2.5)、PM_(10)的浓度在空间分布上趋势一致,均表现为以固定外源点为核心,浓度随距离增加呈极显著梯度递减的趋势,且在中部(约距外源点150~220 m处)消减效率最高,约为全园PM_(2.5)平均消减值的7.5倍,PM_(10)平均消减值的3.8倍;PM_(2.5)、PM_(10)受多种因子影响:与空气温度、距离(主导因子)显著负相关、与相对湿度显著正相关,且PM_(2.5)、PM_(10)对不同因子响应特征存在差异;城市公园不同绿地空间结构对PM_(2.5)、PM_(10)的消减及扩散作用差异显著,受其双重影响,PM_(2.5)、PM_(10)的浓度表现为水体>广场>树林>草坪,其中PM_(2.5)受影响更显著;此外,受各因子和绿地空间结构耦合影响,部分区域PM_(2.5)、PM_(10)分布异常。【结论】以固定外源点为核心,PM_(2.5)、PM_(10)浓度随距离增加呈极显著梯度递减的趋势,且在中部消减效率最高;PM_(2.5)、PM_(10)浓度与相对湿度显著正相关,与空气温度与距离显著负相关,其中PM_(10)对距离和相对湿度响应较为明显,而PM_(2.5)受空气温度影响较大;在随距离变化基础上,不同城市绿地空间结构对PM_(2.5)、PM_(10)消减和扩散作用差异导致了局部分布差异。

基于Twin Builder的110kV油浸式变压器3维磁场降阶模型及损耗分析

为解决3维变压器磁场有限元仿真计算效率低的问题,提出基于本征正交分解法的磁场降阶模型与基于二次多项式的损耗响应面模型。以1台110 kV变压器为算例,首先建立了考虑绕组涡流损耗的变压器磁场仿真模型,通过仿真分析了其在额定工况下的磁场及损耗分布;其次,通过仿真试验设计获取了多组工况下的磁场与损耗数据,在Twin Builder中训练得到变压器磁场的各降阶模块;最后,搭建面向数字孪生应用的变压器3维磁场降阶模型,实现了变压器磁场损耗的快速计算与云图分布的可视化。与计算单数据相比,仿真结果考虑了涡流效应的绕组损耗在靠近端部时有明显升高,最大值分别出现在高、低压绕组两端,约为绕组中部损耗的1.3~1.65倍。基于该磁场结果建立的降阶模型在计算效率方面较全阶模型有显著提升,将实际仿真时间缩短至0.76s,可满足数字孪生应用场景下的磁场快速计算需求。

智能录井技术研究进展及发展展望

录井具有样品条件及制样工序复杂、采集项目多而离散、人工经验依赖性强且人均产值低等特点,亟需加强智能化转型,但相比于其他石油工程技术,智能录井技术进展缓慢,且局限于应用层面。为此,从智能钻井的进展与成效入手,分析了国内外智能钻井在硬件系统、控制系统、应用系统方面的进展与差距;然后,从地质录井、工程录井、智慧平台3个方面分析了智能录井的主要技术进展,包括“数据+”驱动和视觉驱动的岩性识别、流体识别、井下与地面风险识别及预警等。通过对比智能钻井与智能录井的现状,提出智能录井应强化井下智能录井、智能录井机器人等硬件系统及多场数字孪生、多元采集智能控制、多模态录井大模型、智能解释评价等软件系统的研发。同时强调,既要高度重视,又要理性看待智能录井的发展,要在回顾评价、横向对比的基础上,做好战略定位与研发流程优化,实现进度追赶与作用发挥。这些分析与观点,对推动智能录井实现良性、快速发展具有指导意义。

基于商用密码的水利重要数据点面结合安全保护方法

为保障数字孪生流域建设过程中的重要数据安全,针对破解海量高精度数据汇集面临的数据窃取、泄露、损毁等问题隐患开展研究,提出网络安全基础—数据分类分级—数据安全防护的数字孪生流域数据安全总体防护方案。针对数据安全传输、存储、使用中的安全薄弱点,提出全面通用防护和应用内加密相结合的点面结合加密保护方法,利用商用密码技术对数据进行机密性、完整性、可用性保护。本研究方法已在全国水利一张图等重要系统中得到应用,可实现数据安全保护和便捷高效应用平衡,广泛适用于数字孪生流域建设中的水利重要数据全生命周期保护。

基于机器视觉的闸坝表面位移非接触式监测方法

针对闸坝表面位移常规监测方法劳动密度高、监测频次低,且难以实现长期稳定监测等问题,提出一种融合时空特征的闸坝表面位移非接触式智能监测方法。该方法采用人工靶标作为标志物,以摄像机为采集设备,通过无线传输图像信息,利用加权分布的自适应伽马修正(AGCWD)与边缘感知因子改进的加权引导滤波(WGIF)增强低照度图像的特征表达能力,通过计算机搭载基于贝叶斯框架的时空上下文信息(STC)算法深度挖掘靶标图像上下文时空信息,进一步地,引入曲面拟合获取靶标的亚像素级位移时程信息,实现闸坝水平和垂直双向表面位移的亚像素级非接触式监测。实验室与现场试验结果表明,不同实验场景下位移监测数据与校验数据高度一致,误差小于0.05 mm;相比于图像优化处理方法,基于AGCWD与WGIF的图像优化处理方法的峰值信噪比提升2.70%,信息熵增加4.91%,标准差降低2.63%;相比于目标追踪算法,基于曲面拟合的STC目标追踪算法的现场监测数据较同类目标追踪算法精度提升48%,可为闸坝表面位移监测提供高精度的解决方案。

遥感降水降尺度高精度校正及不确定性分析方法

为消除降水场同质部分影响,提升统计降水降尺度结果精度,提出了基于贝叶斯高精度曲面建模(Bayes-HASM)算法的遥感降水降尺度高精度校正方法。该方法通过引入模拟精度更高的高精度曲面建模方法,并结合贝叶斯优化算法,实现了模型参数自动优化选择和高精度降尺度校正,解决了现有降尺度残差校正方法存在的误差和多尺度问题。结果表明:贝叶斯优化使高精度曲面建模的不确定性显著减少;经过Bayes-HASM残差校正后,降尺度结果的散点分布更加接近1∶1线,年、季、月和旬尺度的精度指标均得到了显著的改善,CC和IA指标提高至0.9左右,RMSE下降明显,RB也显著改善。本方法能显著降低模型的不确定性并起到消除降水场同质部分影响的作用,有效提升降水降尺度结果精度。

渐开螺旋面的数字化曲面及其计量特征

真实齿面的数字化重建是虚拟仿真与测量的重要基础,提出了基于几何线特征的渐开线齿轮齿面的数字化曲面构造方法,根据渐开线齿轮齿面的渐开线、螺旋线和接触线三条特征线之间的相交关系划分齿面网格点,分别构造出三角面片组成的渐开螺旋面和双三次NURBS渐开线螺旋面。与三角面片集拟合得到的曲面进行面型拟合特征与拟合精度、特征线拟合特征与拟合精度的比对分析、特征线拟合精度与光顺性的分析计算。分析结果表明,两种数字化曲面具有明显不一样的特征,NURBS渐开螺旋面具有良好的精度和光顺性。

光学成像卫星实景三维技术应用及启示

文章归纳总结了具有实景三维应用能力的光学成像卫星的发展,调研了目前国外卫星实景三维技术应用产品,梳理了近年国外卫星实景三维产品在高精度三维基础数据开发、目标指示等方面的应用,研究了实景三维产品在遥感领域的市场潜力,提出光学成像卫星实景三维技术应用已成为国家的重要数据资源和生产要素,在民商用领域,卫星实景三维技术应用是引领遥感产业跨越式发展的途径之一。

联合无人机影像生成DSM和DOM的多层次建筑物变化检测

随着我国城镇化水平的不断提高,城镇建筑物日新月异,及时、准确地掌握城镇建筑物的变化信息对城镇管理、违章建筑查处及灾害评估有着重要意义。该文提出了一种联合无人机影像生成数字表面模型(digital surface model,DSM)和正射影像(digital orthophoto map,DOM)的多层次建筑物变化检测方法,主要包括4个步骤:①对无人机影像生成的密集点云和DOM进行预处理,生成差分归一化DSM(differential normalized DSM,dnDSM)并提取植被区域;②利用多层高差阈值提取候选变化区域,并在此过程中剔除植被及面积较小区域;③对低层候选变化区域进行连通域分析,对于每个连通对象,利用其较高层的变化检测结果剔除低层中的误检测;④统计每个变化对象的正、负高差值数量关系,确定变化类型。实验结果表明,该文方法不但能够保留较低高差阈值检测到的低矮变化建筑物,而且能够保证高大变化建筑物的正确性、完整性。

基于数字孪生的机场场面滑行冲突预测模型构建与分析

传统机场场面滑行冲突检测主要依靠管制员目视判断冲突风险,随着航空运输量的增长,依靠人工判断方式的短板日益突出,急需一种降低人工依赖的冲突判定方法。目前大多数冲突模型存在模型与场面真实情况交互不及时等问题;因此本文提出一种基于数字孪生的机场场面滑行冲突预测模型,该模型通过物理系统与孪生系统数据交互从而及时对场面冲突进行预测。进一步,考虑孪生系统时延要求,基于4G、5G和AeroMACS(aeronautical mobile airport communications system)等机场场面主流的通信方式,进行了时延建模与分析。仿真结果表明,该模型能预测各冲突类型中航空器到达最小安全距离的时间,并在5G和AeroMACS组网条件下满足典型业务时延(0.5~20 ms),可为机场场面系统的网联化与智能化发展提供技术参考。