计算机辅助外科中手术与计划空间标定以及视觉空间的误差校正

计算机辅助外科(CAS)系统中,多空间集成在一起,为了提高系统的操作精度,需要有效的标定方法校正空间之间的误差.利用机器人上特征在导航系统中视觉空间的运动误差,建立视觉空间与机器人空间的映射关系,递归校正两空间之间的局部转换矩阵.利用局部转换矩阵建立优化方程,求取全局最优转换矩阵.该方法对所有动态、静态误差进行校正.针对手术与计划空间中存在的耦合误差,利用设计的特殊结构力传感器和标定块解耦标定其误差,并根据求取的转换矩阵,调整计划空间中对象的位姿,保证计划空间与手术空间中的对象位姿一致.实验结果表明,动态标定方法可以使视觉空间中的全局误差减少到5个像素,力控标定方法可以使位置误差减小到0.25mm,姿态误差减小到0.1°.     

多假设跟踪的移动机器人SLAM算法

针对基于视觉定位的移动机器人自主定位过程中容易产生多种候选位姿.提出一种基于多假设跟踪的同时定位和地图创建方法.该方法通过提取图像SIFT特征进行视觉量测,修正里程计累计误差,再利用多假设跟踪方法获得当前时刻的最优位姿,实时产生环境的栅格地图,并且随着机器人的位姿变化实时更新.研究结果表明:此算法不仅能够较好地创建环境地图,而且能够有效解决机器人"绑架"问题,提高自主定位精度.     

工业机器人绝对定位误差补偿技术研究进展

 针对航空制造业中工业机器人存在实际位姿与理论位姿偏差的问题,分析了工业机器人绝对定位误差来源,解析其对飞机零部件连接性能产生的影响,在工业机器人绝对定位误差补偿原理和主要步骤分析基础上,阐述运动学建模、位姿测量、运动学参数误差辨识以及误差补偿等关键步骤对工业机器人绝对定位误差补偿的作用及重要性,对比分析了国内外学者在该步骤中涉及的主流算法和技术,归纳总结各步骤中存在的问题和可能的解决方案,探讨了工业机器人离线与在线误差补偿技术中的不足之处,指出工业机器人绝对定位误差补偿技术的发展趋势。     

融合多传感器信息的移动机器人自定位方法

提出一种给定环境模型下移动机器人全局自定位算法,通过融合声纳传感器和视觉传感器的异质传感信息把具有多模态、鲁棒性强的Markov方法和单模态、高效准确的EKF方法组合应用并加以改进,来实现准确和快速的全局定位,同时提高位姿跟踪的准确性.Markov方法中位姿空间的低分辨率离散减小了存储需求,声纳感知模型对位姿空间分布进行初始化并提供了全局的位姿假设,视觉感知模型实现了位姿分布更新,而基于视觉特征的EKF方法则提高了定位的精度.实验结果验证了本方法的有效性.     

多因素影响下的机器人综合位姿误差分析方法

分析了影响机器人位姿精度的主要因素，将各种因素综合为机器人的结构参数误差和运动变量误差，充分考虑关节柔性和连杆柔性对机器人末端位姿精度的影响，建立了通用的机器人综合位姿误差分析模型，并编制了基于Matlab的Windows应用程序．该程序具有较强的通用性，适用于分析由机器人的各种静态误差以及关节柔性和连杆柔性所导致的平面和空间机器人末端执行器的综合位姿误差。     

基于视觉的六自由度机械臂运动学参数辨识

提出一种新型低成本的基于单目视觉的机器人末端位姿测量方法,设计并实现了六自由度机械臂的运动学参数辨识。采用分级测量方法和标定板绝对编码方法,解决了当前视觉测量过程中测量范围小、测量精度受相机畸变影响大等问题;使用基于位置误差的运动学参数辨识模型和单目视觉测量系统,简化了机器人的标定过程。最后,通过实验验证了方案的实用性和有效性。     

主-从式手术机器人运动一致性分析

采用成熟的机器人误差理论建立了主-从手术机器人位姿误差模型,开发了基于MATLAB的位姿误差计算程序.采用蒙特卡罗法绘制了最大位姿误差图谱,对两种主手与三种从手机器人进行了仿真计算和运动一致性分析,给出了运动一致性条件,为进行主-从操作机器人精度设计提供了理论依据.     

一种智能空间辅助的家庭服务机器人SLAM方法

在单机器人SLAM过程中,定位误差和建图误差随机器人运动距离增大而增大。为了有效降低SLAM误差,本文提出了一种智能空间辅助的家庭服务机器人SLAM方法。基于Rao-Blackwellized粒子滤波思想,机器人定位和建图问题被分解为两个独立环节,首先,联合机器人控制量和智能空间摄像机网络的观测值估计机器人位姿,给出了位姿粒子的采样提议分布和权值更新公式;然后,机器人利用自身位姿及对目标的观测来构建环境地图。仿真实验表明本方法有效提高了机器人的定位精度,进而得到了更加精确的环境地图。     

一种基于视觉测量的大型碟式聚光器 镜面单元位姿调节方法

根据大功率碟式聚光器镜面单元结构特点及在线安装过程中对镜面单元位姿快速检测、高效调节和精确定位的需要,提出了一种基于三目视觉测量和机器人辅助安装的镜面单元位姿调节方法.建立了任一镜面单元角点空间坐标方程,设计了镜面单元位姿调节系统结构,并明确了相应调节方法与步骤.以38 k W碟式聚光器为例,对镜面单元不同位姿进行了光学计算,分析了视觉测误差和镜面单元制造误差等因素对镜面单元位姿调节的影响.结果表明,基于视觉测量的调节方法,在不考虑其他误差情况时,当视觉测量误差和镜面单元制造误差的综合误差控制在±2 mm内,能满足镜面单元位姿调节精度要求.     

结合精度补偿的机器人优化手眼标定方法

为了解决制造现场机器人高精度视觉测量定位的问题提出了一种结合模型精度补偿的机器人方位与手眼关系同步标定方法。该方法首先将视觉系统与机器人之间的位姿关系即手眼关系以及标定板与机器人坐标系的空间转换关系作为待优化求解对象,用齐次坐标矩阵分别表示机器人运动学正解以及视觉系统与标定板之间的位姿关系,进而构建闭环的机器人手眼关系优化方程;然后,使用三维旋转群表示旋转矩阵,建立了标定模型方程,用非线性全局优化的方式同步得到标定方程中矩阵的旋转和平移初始解,采用最小化相机的重投影误差提高了标定精度;最后,使用机器人运动学标定设备提升了本体的模型精度,再进行视觉标定得到了更准确的标定结果。实验结果表明:该标定方法只需提前示教若干点即可自动完成,操作简易高效;在补偿了机器人本体的臂长和关节零位误差后,算法精度从0.15mm提升至0.10mm。与经典的手眼标定方法相比,所提方法在不同测试数据集下的标定精度和稳定性均最优。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that