在三维地理信息系统(Geography Information System,GIS)中,高效、逼真地模拟现实场景是研究的重要内容之一。因此如何获得精确的场景数据和逼真的场景显示是研究的关键问题。该文对三维地理信息系统中模型的数据采集和构建方法进行了研...在三维地理信息系统(Geography Information System,GIS)中,高效、逼真地模拟现实场景是研究的重要内容之一。因此如何获得精确的场景数据和逼真的场景显示是研究的关键问题。该文对三维地理信息系统中模型的数据采集和构建方法进行了研究,采用OPENGL三维图形技术和基于四叉树的区域分层显示技术,实现了一个可针对具体模型操作和查询分析的高逼真度三维地理信息系统。并在系统中完成了虚拟校园一角的设计。实践证明,该系统所采用的方法和技术能够精确高效的虚拟真实场景,满足虚拟校园或虚拟小区规划的要求。展开更多
Smoothly attaching the stretchable epidermal electronic devices(EEDs) onto the skin surface is highly desired to improve the measurement accuracy of electrophysiological signal.The paper presents an analytical approac...Smoothly attaching the stretchable epidermal electronic devices(EEDs) onto the skin surface is highly desired to improve the measurement accuracy of electrophysiological signal.The paper presents an analytical approach to study interfacial mechanics of the 2D planar EEDs on the checkerboard buckling patterns of human skin.Energy variation method is proposed to determine a criterion whether EEDs laminate conformally onto the skin surface under undeformed and stretched cases.EEDs with low bending stiffness(thin,soft devices/backing layer),smooth and soft skin,and strong adhesion promote conformal contact.Furthermore,the adhesion energy at the EED/skin interface is measured by the homemade peeling experiment platform with different substrate thicknesses and areal coverages.The upper limit of the areal coverage for EED conformal contact with the skin is proposed with given EED/skin properties.Conformability of EEDs are validated by experiments with different substrate thickness,areal coverage and external loadings.It provides a design guideline for EED to conformally contact with the skin surface for more accurate biological signal monitoring.展开更多
The kinematic accuracy of space manipulator determines whether the spacecraft performs normally or not. Problems pertaining to structural deformation have received increased attention in recent times. In the space man...The kinematic accuracy of space manipulator determines whether the spacecraft performs normally or not. Problems pertaining to structural deformation have received increased attention in recent times. In the space manipulator systems, flexible arms and joints can induce drastic dynamic instabilities. In applications such as the space station, kinematic error due to structural deformation can jointly affect the performance characteristics. And it is crucial for accuracy control of space manipulator to establish a precision index. Here we analyze the dynamics characteristic of flexible space manipulator considering the hysteresis of harmonic reducer based on method of nonconstraint boundary modal. For the sake of describing the output accuracy, we integrate the method of analytic hierarchy process(AHP) to establish a comprehensive evaluation index. A numerical simulation is performed to analyze the nonlinear dynamic characteristics of space manipulator with harmonic reducer. With the analysis of accuracy assessment, the relation among the hysteresis angle, rigidity and output accuracy is revealed. Considering the elastic modulus of flexible space manipulator and the hysteresis angle of harmonic reducer, we conduct an evaluation of output characteristics of flexible space manipulator with the proposed comprehensive evaluation index. The accuracy evaluation of output characteristics based on the proposed comprehensive evaluation index is implemented in the initial stage of space manipulator's design, which can not only solve the problems existing in the design but also save cost savings for ground tests. The results can be used in designing and optimizing future space manipulators, which may provide valuable references for design and thermal control of the space manipulator.展开更多
文摘在三维地理信息系统(Geography Information System,GIS)中,高效、逼真地模拟现实场景是研究的重要内容之一。因此如何获得精确的场景数据和逼真的场景显示是研究的关键问题。该文对三维地理信息系统中模型的数据采集和构建方法进行了研究,采用OPENGL三维图形技术和基于四叉树的区域分层显示技术,实现了一个可针对具体模型操作和查询分析的高逼真度三维地理信息系统。并在系统中完成了虚拟校园一角的设计。实践证明,该系统所采用的方法和技术能够精确高效的虚拟真实场景,满足虚拟校园或虚拟小区规划的要求。
文摘Smoothly attaching the stretchable epidermal electronic devices(EEDs) onto the skin surface is highly desired to improve the measurement accuracy of electrophysiological signal.The paper presents an analytical approach to study interfacial mechanics of the 2D planar EEDs on the checkerboard buckling patterns of human skin.Energy variation method is proposed to determine a criterion whether EEDs laminate conformally onto the skin surface under undeformed and stretched cases.EEDs with low bending stiffness(thin,soft devices/backing layer),smooth and soft skin,and strong adhesion promote conformal contact.Furthermore,the adhesion energy at the EED/skin interface is measured by the homemade peeling experiment platform with different substrate thicknesses and areal coverages.The upper limit of the areal coverage for EED conformal contact with the skin is proposed with given EED/skin properties.Conformability of EEDs are validated by experiments with different substrate thickness,areal coverage and external loadings.It provides a design guideline for EED to conformally contact with the skin surface for more accurate biological signal monitoring.
文摘The kinematic accuracy of space manipulator determines whether the spacecraft performs normally or not. Problems pertaining to structural deformation have received increased attention in recent times. In the space manipulator systems, flexible arms and joints can induce drastic dynamic instabilities. In applications such as the space station, kinematic error due to structural deformation can jointly affect the performance characteristics. And it is crucial for accuracy control of space manipulator to establish a precision index. Here we analyze the dynamics characteristic of flexible space manipulator considering the hysteresis of harmonic reducer based on method of nonconstraint boundary modal. For the sake of describing the output accuracy, we integrate the method of analytic hierarchy process(AHP) to establish a comprehensive evaluation index. A numerical simulation is performed to analyze the nonlinear dynamic characteristics of space manipulator with harmonic reducer. With the analysis of accuracy assessment, the relation among the hysteresis angle, rigidity and output accuracy is revealed. Considering the elastic modulus of flexible space manipulator and the hysteresis angle of harmonic reducer, we conduct an evaluation of output characteristics of flexible space manipulator with the proposed comprehensive evaluation index. The accuracy evaluation of output characteristics based on the proposed comprehensive evaluation index is implemented in the initial stage of space manipulator's design, which can not only solve the problems existing in the design but also save cost savings for ground tests. The results can be used in designing and optimizing future space manipulators, which may provide valuable references for design and thermal control of the space manipulator.
