Interaction of a circular cavity and a beeline crack in right-angle plane impacted by SH-wave

The problem of scattering of SH-wave by a circular cavity and an arbitrary beeline crack in right-angle plane was investigated using the methods of Green's function,complex variables and muti-polar coordinates.Firstly,we constructed a suitable Green's function,which is an essential solution to the displacement field for the elastic right-angle plane possessing a circular cavity while bearing out-of-plane harmonic line source load at arbitrary point.Secondly,based on the method of crack-division,integration for solution was established,then expressions of displacement and stress were obtained while crack and circular cavities were both in existence.Finally,the dynamic stress concentration factor around the circular cavity and the dynamic stress intensity factor at crack tip were discussed to the cases of different parameters in numerical examples.Calculation results show that the crack produces adverse engineering influence on both of the dynamic stress concentration factor and the dynamic stress intensity factor.

COORDINATES OF PRINCIPAL STRESSES FOR ELASTIC PLANE PROBLEM

In this paper, the equilibrium equations on orthogonal curve coordinates made of curves of principal stresses are disscused and their properties in process of solution are presented through a simple example. Therefore, it is deduced that there is another way to solve problems in elasticity, i.e., by assumption of orthogonal curves of principal stresses.

SCATTERING OF CIRCULAR CAVITY IN RIGHT-ANGLE PLANAR SPACE TO STEADY SH-WAVE

Complex function method and multi-polar coordinate transformation technology are used here to study scattering of circular cavity in right-angle planar space to SH-wave with out-of-plane loading on the horizontal straight boundary. At first, Green function of right-angle planar space which has no circular cavity is constructed; then the scattering solution which satisfies the free stress conditions of the two right-angle boundaries with the circular cavity existing in the space is formulated. Therefore, the total displacement field can be constructed using overlapping principle. An infinite algebraic equations of unknown coefficients existing in the scattering solution field can be gained using multi-polar coordinate and the free stress condition at the boundary of the circular cavity. It can be solved by using limit items in the infinite series which can give a high computation precision. An example is given to illustrate the variations of the tangential stress at the boundary of the circular cavity due to different dimensionless wave numbers, the location of the circular cavity, the loading center and the distributing range of the out-of-plane loading. The results show the efficiency and effectiveness of the mothod introduced here.

Three-dimensional coordinates test method with uncertain projectile proximity explosion position based on dynamic seven photoelectric detection screen

To objectively obtain the three-dimensional coordinates of the projectile fuze proximity explosion when projectile intersects the head of missile target, we propose a dynamic seven photoelectric detection screen test method, which is made up of six plane detection screens and a flash photoelectric dynamic detection screen. The three-dimensional coordinates calculation model of the projectile proximity explosion position based on seven plane detection screens with dynamic characteristics is established.According to the relation of the dynamic seven photoelectric detection screen planes and the time values,the analytical function of the projectile proximity explosion position parameters under non-linear motion is derived. The projectile signal filtering method based on discrete wavelet transform is explored in this work. Additionally, the projectile signal recognition algorithm using an improved particle swarm is proposed. Based on the characteristics of the time duration and the signal peak error for the projectile passing through the detection screen, the signals attribution of the same projectile passing through six detection screens are analyzed for obtaining precise time values of the same projectile passing through the detection screens. On the basis of the projectile fuze proximity explosion test, the linear motion model and the proposed non-linear motion model are used to calculate and compare the same group of projectiles proximity explosion position parameters. The comparison of test results verifies that the proposed test method and calculation model in this work accurately obtain the actual projectile proximity explosion position parameters.

Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

The application of fiber reinforced plastic（FRP）,including carbon FRP and glass FRP,for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement（EBR） and near-surface mounted（NSM） strengthening techniques.This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods,including externally-bonded and near-surface mounted FRP,to study the strain coordination of the FRP and steel rebar of the RC beam.Since there is relative slipping between the RC beam and the FRP,the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis;that is,the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height（h 0） of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of the FRP and steel rebar satisfies the equation：ε FRP =βε steel,and the value of β is equal to 1.1-1.3 according to the test results.

An Algorithm for Finding Internal Faces Based on the 3D Coordinates

This paper presents a direct method to find the internal faces. It uses four sets of information： get the coordinates of each point on the 3D composite objects; （~）based on the 3D coordinates to calculate all the plane equation of two objects; （~）calculate all the intersecting lines of the two objects and exclude the intersecting lines which are not within the scope of the plane;finding the internal face, the remaining intersecting lines formed the plane is the internal face of the two objects. We proposed a new algorithm for finding internal faces. This algorithm could be adapted to any regular composite objects .The algorithm works well for finding internal faces.

A general metrology of stress on crystalline silicon with random crystal plane by using micro-Raman spectroscopy

The requirement of stress analysis and measurement is increasing with the great development of heterogeneous structures and strain engineering in the field of semiconductors.Micro-Raman spectroscopy is an effective method for the measurement of intrinsic stress in semiconductor structures.However,most existing applications of Raman-stress measurement use the classical model established on the (001) crystal plane.A non-negligible error may be introduced when the Raman data are detected on surfaces/cross-sections of different crystal planes.Owing to crystal symmetry,the mechanical,physical and optical parameters of different crystal planes show obvious anisotropy,leading to the Raman-mechanical relationship dissimilarity on the different crystal planes.In this work,a general model of stress measurement on crystalline silicon with an arbitrary crystal plane was presented based on the elastic mechanics,the lattice dynamics and the Raman selection rule.The wavenumberstress factor that is determined by the proposed method is suitable for the measured crystal plane.Detailed examples for some specific crystal planes were provided and the theoretical results were verified by experiments.

考虑结构面震动劣化效应的岩质边坡块体动力稳定性评价

为解决岩质边坡块体在地震作用下的动力稳定性评价问题,基于结构面的循环剪切数值试验研究结构面的震动劣化效应,从而构建结构面震动劣化数学模型;结合坐标投影原理提出考虑结构面强度震动劣化效应的块体动力稳定性系数计算方法;基于数值分析法研究地震波波动特性对岩质边坡块体稳定性的影响,并进一步基于突变理论提出位移动力响应放大系数突变判据,最后形成一套以块体动力稳定性系数时程曲线和位移动力响应放大系数共同评价块体动力稳定性的评价体系,拓展地震作用下块体动力稳定性评价新思路。研究表明,结构面震动劣化效应不仅受循环剪切幅值、循环剪切次数及相对运动速度影响,还与起伏角度密切相关;通过算例证实了考虑结构面震动劣化的块体动力稳定性系数计算方法的准确性,所提出的以块体动力稳定性系数时程曲线和位移动力响应放大系数的共同评价体系更加安全可靠,将促进块体动力稳定性理论的发展,对边坡地质灾害的防治具有重要的科学意义和应用价值。

合成孔径雷达快速后向投影算法综述

后向投影(BP)算法是合成孔径雷达成像算法发展的重要方向之一。然而,由于BP算法具有较大的计算量,阻碍了其在工程应用上的发展。因此,近年来如何有效地提高BP算法的运算效率受到了广泛的重视。该文讨论了基于多种成像面坐标系的快速BP算法,包括距离-方位平面坐标系、地平面坐标系和非欧氏坐标系。该文首先简要介绍了原始BP算法的原理和不同坐标系对加速BP算法的影响,并对BP算法的发展历程进行梳理。然后讨论了基于不同成像面坐标系的快速BP算法的研究进展,并重点介绍了作者所在研究团队近年来在快速BP成像方面完成的研究工作。最后介绍了快速BP算法在工程上的应用,并展望了未来快速BP成像算法的研究发展趋势。

Phase-plane analysis of conserved higher-order traffic flow model

The phase-plane analysis is used to study the traveling wave solution of a recently proposed higher-order traffic flow model under the Lagrange coordinate system. The analysis identifies the types and stabilities of the equilibrium solutions, and the overall distribution structure of the nearby solutions is drawn in the phase plane for the further analysis and comparison. The analytical and numerical results are in agreement, and may help to explain the simulated phenomena, such as the stop-and-go wave and oscillation near a bottleneck. The findings demonstrate the model ability to describe the complexity of congested traffic.

降雨作用下考虑结构面劣化的边坡块体稳定性评价

降雨是诱发边坡失稳,发生崩塌、落石、滑坡的一个主要诱因,降雨作用下结构面强度会发生劣化,导致边坡块体失稳塌落,引起地质灾害,对人民生命财产构成严重威胁。基于离散元数值分析方法,考虑降雨作用对结构面抗剪强度的影响,分析结构面强度参数劣化及孔隙水压力变化规律,建立抗剪强度劣化模型;结合坐标投影原理提出考虑降雨作用下结构面强度劣化效应的块体稳定性系数计算方法;基于有限元分析方法研究降雨强度与降雨历时对岩质边坡块体稳定性的影响,并进一步分析稳定性系数与降雨强度及降雨历时的关系,提出降雨作用下考虑结构面劣化的边坡块体稳定性评价方法。研究表明,不同含水率作用下结构面的抗剪强度劣化不仅受黏聚力和内摩擦角影响,还与孔隙水压力有关,针对单滑面和双滑面型块体构建了考虑结构面降雨劣化的稳定性分析数学模型,提出的以降雨时长、降雨强度和块体稳定性关系曲线的共同评价体系可为边坡块体稳定性评价提供科学依据,并推动边坡地质灾害防治和工程建设发展。

基于相平面的滑模/模糊协调控制方法研究

针对结构化道路下车辆高速、紧急、突发障碍物等工况下所带来的无人车路径规划中的失稳问题,提出了一种模糊控制与滑模变结构控制协调控制的策略。首先,采用了基于五次多项式的路径规划方法。采用一种基于MPC模型预测控制的车辆轨迹跟踪控制策略,通过控制前轮转角主动转向来控制车辆换道。提出了一种滑模控制器与模糊控制器协调控制的控制策略,通过相平面法确定稳定边界方程,然后将边界方程介入控制器,并通过差动制动将横摆力矩合理分配到各车轮。通过Matlab与Carsim联合仿真,设计了不同的仿真工况。结果表明,车辆在高速、紧急的行驶工况下,这里所设计的协调控制方法,能够有效的提高车辆的轨迹跟踪性能与车辆路径规划中的稳定性和安全性。

侧风干扰下汽车稳定性控制研究

文章针对高速行驶的汽车在侧风干扰下易发生横摆失稳与驶离预定路径的问题,建立了考虑侧风作用的整车八自由度动力学模型,并利用相平面法,识别侧风环境中汽车所处的状态,设计了主动前轮转向(AFS)与直接横摆力矩(DYC)协调控制器,对侧风环境中汽车行驶进行稳定性控制。在侧风干扰工况下,对控制算法进行仿真验证,结果表明:具有AFS与DYC协调控制器车辆的侧向位移小于无控制及单一控制器的车辆,横摆角速度、质心侧偏角和侧向加速度均得到明显改善,提高了车辆在侧风环境中行驶的安全性和稳定性。

基于CGCS2000的相对独立平面坐标系建立和分析

随着2000国家大地坐标系的全面启用,原有地方坐标系已无法满足现代城市建设和社会发展的需要。论文阐述了地方坐标系建立原则和方法,结合投影变形理论对相对独立平面坐标系建立影响因素中中央子午线和投影面的选取进行了详细分析,并以淮安区域为例,结合淮安DEM,详细分析了淮安2000坐标系在淮安市各区县的投影变形情况,同时用格网占比法分析了其与原有坐标系的面积变化。结果表明,淮安2000坐标系在淮安区域内小于2.5 cm/km面积占淮安陆域面积的99.8%,最大投影变形为3.303 cm/km,位于丘陵区域;与原有坐标系相比,在面积变化上优于万分之一,具有良好的适用性。

磨削机器人的轨迹规划

为了增强机器人在打磨操作中的稳定性和精确度,文中对其轨迹规划设计进行了研究。针对关节面空间,探讨了三次多项式插值、五次多项式插值和B样条曲线插值方法;针对平面直角坐标空间,研究了平面直角坐标空间轨迹规划方法。同时对比分析了它们的特点,为磨削机器人轨迹规划方法的选择提供了参考。

线状工程中平面坐标系构建研究

为了提升线状工程测量的精度与效率,构建准确的平面坐标系,本文通过介绍GPS数据处理技术,详细分析了方向与距离观测值的两化改正方法。在此基础上,探讨了基于高斯投影的线状工程测量原理,并提出了建立工程渐变平面坐标系的方案。研究结果表明,通过实施两化改正和采用高斯投影方法,能够显著提高线状工程测量的准确性和可靠性,为工程设计与施工提供了有力的技术支持。同时,构建渐变平面坐标系可以有效反映线状工程的形变规律,为工程监测与评估提供了重要依据。

基于模数驱动与轴面协同理论的智能高速铁路施工与运营阶段管理研究

随着高速铁路建设不断发展,智能高速铁路概念孕育而出。着眼于智能高速铁路实施层面,结合我国高速铁路智能化特点和需求,引入模数驱动与轴面协同概念,从全生命周期角度,提出了智能高速铁路在施工阶段和运营阶段的管理策略。在施工阶段,以全生命周期效能最优为目标,综合考虑成本、安全、风险等因素,贯穿形成时间轴,实现多个业务要素的整体协同、综合最优。在运营阶段,聚焦动车组检修备件管理场景,探究智能高速铁路资产的全生命周期一体化管理模式,并设计一套科学、合理的动车组检修备件管理评价指标体系,以推动动车组检修备件的运营效率提升。研究成果可以为智能高速铁路未来发展提供理论支撑和方向指导。

复杂地形条件下公路工程平面坐标系的建立方法研究

为满足公路工程的勘察设计及后期现场施工的需要,建立适宜的平面坐标系是一项极具必要性与重要性的工作。基于高斯投影变形的2个主要影响因素以及二者之和可部分抵消的特征,结合实例分析了复杂地形条件下公路工程平面坐标系的建立过程;同时,为了克服常规方法建立过程存在以平均代表整体、变形检验方式又存在“以点代面”的局限性,研究了应用DEM检验投影变形的方法,可实现全测区范围内投影变形量的统计分析与可视化展示,为在复杂地形条件下建立公路工程平面坐标系提供了参考。实例表明该方法在复杂地形条件下是适用的、有效的,具有一定的理论与现实意义。

探索大城市边缘区中村庄规划的编制和实施——以广州市番禺区为例

城镇化趋势明显、城乡发展混合的大城市边缘区,其村庄发展及城乡问题比一般乡村地区更为复杂。文章分析了2007年以来广州市番禺区开展的两轮村庄规划实践,结合国土空间规划体系的语境和“实用性”村庄规划要求,对大城市边缘区内村庄规划编制如何协调城乡矛盾、提升规划实用性、解决落地难问题、提升乡村治理水平等方面提出建议。

极限工况下AFS与DYC可拓协调控制

主动前轮转向系统(AFS)和直接横摆力矩控制(DYC)集成控制可提高商用货车的操纵稳定性。由于主动前轮转向在轮胎非线性区作用效果有限,与直接横摆力矩控制简单叠加的控制效果不一定能达到预期,为此这里设计了可拓协调控制系统。该系统分为上、中、下三层,上层为AFS与DYC协调切换控制层。采用试验法得到前轮临界转角,根据线性二自由度车辆模型反推临界转角下的稳态质心侧偏角,结合车辆实际质心侧偏角及其速度的相平面稳定域将相平面图分区,设计了3种不同协调控制策略;中层是基于指数趋近律设计的AFS与DYC滑模控制器,可得到前轮附加转角和附加横摆力矩;附加横摆力矩由下层控制器根据车辆实时状态进行制动力分配。采用TruckSim、Matlab/Simulink建立联合仿真平台,在极限工况下进行仿真验证可拓协调控制系统。仿真结果得到最优可拓协调策略,该协调控制弥补了AFS/DYC单一控制的缺陷,可保证车辆的操纵稳定性和行驶安全性。