非量测相机以价格低、体积小、使用灵活等优势被广泛应用于高精度测量工作中,但相机标定结果对测量精度影响较大,针对现有相机标定方法存在着精度不够或标定效率不高等问题,文章提出一种联合加速分割检测特征(features from accelerated...非量测相机以价格低、体积小、使用灵活等优势被广泛应用于高精度测量工作中,但相机标定结果对测量精度影响较大,针对现有相机标定方法存在着精度不够或标定效率不高等问题,文章提出一种联合加速分割检测特征(features from accelerated segment test,FAST)算法和双像光束法平差的相机标定方法。首先利用FAST算法对像片标志点自动提取,利用直接线性变换方法解得相机内、外参数初值;然后基于固定基线长度约束的双像光束法平差模型解算相机相关参数,并通过分类阈值方法提高模型收敛效率。结果表明:该方法相较于普通双像光束法平差的精度有所提升,其标定后的中误差达到0.0064 mm,且实现了相机标定流程的半自动化,提高了作业效率,有望应用于实际场景的相机标定作业。展开更多
目的推动印刷行业朝更高效的方向迈进,提高印刷设备的易操作性和视觉识别性。方法将Kano和FAST(Function Analysis System Technique)模型引入瓦楞纸激光打印设备设计的前期应用需求分析中,通过问卷的方法获取用户的基本要求,并划分为...目的推动印刷行业朝更高效的方向迈进,提高印刷设备的易操作性和视觉识别性。方法将Kano和FAST(Function Analysis System Technique)模型引入瓦楞纸激光打印设备设计的前期应用需求分析中,通过问卷的方法获取用户的基本要求,并划分为几个子类型,进而建立Kano的二维功能属性模型。采用FAST法建立功能树,辅助使用Kano模型,从而更精准地分析用户需求,并更好地根据其需求进行优化设计。结果综合运用设计原理,针对性地挖掘瓦楞纸激光印刷设备在造型识别性、操作易用性、生产安全性上存在的问题,进而输出更优解。结论该设计方法的引入有助于为同类型的印刷设备设计提供参考,并引起更多相关厂家的重视,推动印刷行业向更积极的方向发展。展开更多
Fast computation of the landing footprint of a space-to-ground vehicle is a basic requirement for the deployment of parking orbits, as well as for enabling decision makers to develop real-time programs of transfer tra...Fast computation of the landing footprint of a space-to-ground vehicle is a basic requirement for the deployment of parking orbits, as well as for enabling decision makers to develop real-time programs of transfer trajectories. In order to address the usually slow computational time for the determination of the landing footprint of a space-to-ground vehicle under finite thrust, this work proposes a method that uses polynomial equations to describe the boundaries of the landing footprint and uses back propagation(BP) neural networks to quickly determine the landing footprint of the space-to-ground vehicle. First, given orbital parameters and a manoeuvre moment, the solution model of the landing footprint of a space-to-ground vehicle under finite thrust is established. Second, given arbitrary orbital parameters and an arbitrary manoeuvre moment, a fast computational model for the landing footprint of a space-to-ground vehicle based on BP neural networks is provided.Finally, the simulation results demonstrate that under the premise of ensuring accuracy, the proposed method can quickly determine the landing footprint of a space-to-ground vehicle with arbitrary orbital parameters and arbitrary manoeuvre moments. The proposed fast computational method for determining a landing footprint lays a foundation for the parking-orbit configuration and supports the design of real-time transfer trajectories.展开更多
A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditiona...A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.展开更多
针对自由表面流动与弹性结构的流固耦合计算效率低、计算耗时长的问题,将流体体积法与基于结构-虚拟弹性体的快速动网格方法相结合,发展了一种适用于自由表面流动的高效流固耦合方法。使用流体体积(volume of fluid,VOF)法对流体自由表...针对自由表面流动与弹性结构的流固耦合计算效率低、计算耗时长的问题,将流体体积法与基于结构-虚拟弹性体的快速动网格方法相结合,发展了一种适用于自由表面流动的高效流固耦合方法。使用流体体积(volume of fluid,VOF)法对流体自由表面进行追踪;将流体域视为虚拟弹性体并构建结构-虚拟弹性体系统,以流固耦合界面的多相流体力为激励求解系统的动力学方程得到结构振动位移和流场网格变形;在每一个时间步内依次求解流体流动、结构变形和流场动网格,实现流固耦合计算。基于发展的方法计算了溃坝水流冲击下弹性挡板的流固耦合响应,得到了溃坝水流的自由液面和弹性挡板的运动行为,结果表明:自由液面演变和弹性挡板振动位移的计算结果与已有算法的结果吻合良好;在同等网格规模下,与已有算法相比本文方法可减少33.3%的计算时间;在水流冲击作用下,弹性挡板向冲击侧小幅弯曲。随后水流沿挡板左侧上升并形成射流,挡板向另一侧大幅弯曲。最后由于两侧流体的阻尼,挡板振幅逐渐衰减。展开更多
文摘目的推动印刷行业朝更高效的方向迈进,提高印刷设备的易操作性和视觉识别性。方法将Kano和FAST(Function Analysis System Technique)模型引入瓦楞纸激光打印设备设计的前期应用需求分析中,通过问卷的方法获取用户的基本要求,并划分为几个子类型,进而建立Kano的二维功能属性模型。采用FAST法建立功能树,辅助使用Kano模型,从而更精准地分析用户需求,并更好地根据其需求进行优化设计。结果综合运用设计原理,针对性地挖掘瓦楞纸激光印刷设备在造型识别性、操作易用性、生产安全性上存在的问题,进而输出更优解。结论该设计方法的引入有助于为同类型的印刷设备设计提供参考,并引起更多相关厂家的重视,推动印刷行业向更积极的方向发展。
基金supported by the National Natural Science Foundation of China (61603398)。
文摘Fast computation of the landing footprint of a space-to-ground vehicle is a basic requirement for the deployment of parking orbits, as well as for enabling decision makers to develop real-time programs of transfer trajectories. In order to address the usually slow computational time for the determination of the landing footprint of a space-to-ground vehicle under finite thrust, this work proposes a method that uses polynomial equations to describe the boundaries of the landing footprint and uses back propagation(BP) neural networks to quickly determine the landing footprint of the space-to-ground vehicle. First, given orbital parameters and a manoeuvre moment, the solution model of the landing footprint of a space-to-ground vehicle under finite thrust is established. Second, given arbitrary orbital parameters and an arbitrary manoeuvre moment, a fast computational model for the landing footprint of a space-to-ground vehicle based on BP neural networks is provided.Finally, the simulation results demonstrate that under the premise of ensuring accuracy, the proposed method can quickly determine the landing footprint of a space-to-ground vehicle with arbitrary orbital parameters and arbitrary manoeuvre moments. The proposed fast computational method for determining a landing footprint lays a foundation for the parking-orbit configuration and supports the design of real-time transfer trajectories.
基金Project(Z110803)supported by the State Key Laboratory of Geomechanics and Geotechnical Engineering,ChinaProject(2008AA062303)supported by the National High Technology Research and Development Program of China
文摘A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.
文摘针对自由表面流动与弹性结构的流固耦合计算效率低、计算耗时长的问题,将流体体积法与基于结构-虚拟弹性体的快速动网格方法相结合,发展了一种适用于自由表面流动的高效流固耦合方法。使用流体体积(volume of fluid,VOF)法对流体自由表面进行追踪;将流体域视为虚拟弹性体并构建结构-虚拟弹性体系统,以流固耦合界面的多相流体力为激励求解系统的动力学方程得到结构振动位移和流场网格变形;在每一个时间步内依次求解流体流动、结构变形和流场动网格,实现流固耦合计算。基于发展的方法计算了溃坝水流冲击下弹性挡板的流固耦合响应,得到了溃坝水流的自由液面和弹性挡板的运动行为,结果表明:自由液面演变和弹性挡板振动位移的计算结果与已有算法的结果吻合良好;在同等网格规模下,与已有算法相比本文方法可减少33.3%的计算时间;在水流冲击作用下,弹性挡板向冲击侧小幅弯曲。随后水流沿挡板左侧上升并形成射流,挡板向另一侧大幅弯曲。最后由于两侧流体的阻尼,挡板振幅逐渐衰减。
