Vertical coherency function model of spatial ground motion

Many studies have focused on horizontal ground motion, resulting in many coherency functions for horizontal ground motion while neglecting related problems arising from vertical ground motion. However, seismic events have demonstrated that the vertical components of ground motion sometimes govern the ultimate failure of structures. In this paper, a vertical coherency function model of spatial ground motion is proposed based on the Hao model and SMART 1 array records, and the validity of the model is demonstrated. The vertical coherency function model of spatial ground motion is also compared with the horizontal coherency function model, indicating that neither model exhibits isotropic characteristics. The value of the vertical coherency function has little correlation with that of the horizontal coherency function. However, the coherence of the vertical ground motion between a pair of stations decreases with their projection distance and the frequency of the ground motion. When the projection distance in the wave direction is greater than 800 meters, the coherency between the two points can be neglected.

Running safety assessment of a train traversing a three-tower cable-stayed bridge under spatially varying ground motion

To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge,a 3D train–track–bridge coupled model is established for accurately simulating the train–bridge interaction under earthquake excitation,which is made up of a vehicle model built by multi-body dynamics,a track–bridge finite element model,and a 3D rolling wheel–rail contact model.A conditional simulation method,which takes into consideration the wave passage effect,incoherence effect,and site-response effect,is adopted to simulate the spatially varying ground motion under different soil conditions.The multi-time-step method previously proposed by the authors is also adopted to improve computational efficiency.The dynamic responses of the train running on a three-tower cablestayed bridge are calculated with differing earthquake excitations and train speeds.The results indicate that(1)the earthquake excitation significantly increases the responses of the train–bridge system,but at a design speed,all the running safety indices meet the code requirements;(2)the incoherence and site-response effects should also be considered in the seismic analysis for long-span bridges though there is no fixed pattern for determining their influences;(3)different train speeds that vary the vibration characteristics of the train–bridge system affect the vibration frequencies of the car body and bridge.

Simulation of multi-support depth-varying earthquake ground motions within heterogeneous onshore and offshore sites

This paper presents a novel approach to model and simulate the multi-support depth-varying seismic motions（MDSMs） within heterogeneous offshore and onshore sites.Based on 1 D wave propagation theory,the three-dimensional ground motion transfer functions on the surface or within an offshore or onshore site are derived by considering the effects of seawater and porous soils on the propagation of seismic P waves.Moreover,the depth-varying and spatial variation properties of seismic ground motions are considered in the ground motion simulation.Using the obtained transfer functions at any locations within a site,the offshore or onshore depth-varying seismic motions are stochastically simulated based on the spectral representation method（SRM）.The traditional approaches for simulating spatially varying ground motions are improved and extended to generate MDSMs within multiple offshore and onshore sites.The simulation results show that the PSD functions and coherency losses of the generated MDSMs are compatible with respective target values,which fully validates the effectiveness of the proposed simulation method.The synthesized MDSMs can provide strong support for the precise seismic response prediction and performance-based design of both offshore and onshore large-span engineering structures.

A coherency function model of ground motion at base rock corresponding to strike-slip fault

At present, the method to study spatial variation of ground motions is statistic analysis based on dense array re-cords such as SMART-1 array, etc. For lacking of information of ground motions, there is no coherency function model of base rock and different style site. Spatial variation of ground motions in elastic media is analyzed by deterministic method in this paper. Taking elastic half-space model with dislocation source of fault, near-field ground motions are simulated. This model takes strike-slip fault and earth media into account. A coherency func-tion is proposed for base rock site.

Robot motion control in mobile environment

With the problem of robot motion control in dynamic environment represented by mobile obstacles,working pieces and external mechanisms considered, a relevant control actions design procedure has been pro-posed to provide coordination of robot motions with respect to the moving external objects so that an extension ofrobot spatial motion techniques and active robotic strategies based on approaches of nonlinear control theory canbe achieved.

新型步态辅助医学诊疗系统的应用与验证

目的应用不依赖穿戴设备的新型步态辅助医学诊疗系统,验证其可行性、实用性、准确性。方法选取60名受试者为研究对象,按自身对照研究方法先后用新型步态辅助医学诊疗系统与Vicon运动捕捉系统测试步态,受试者以3种速度行走(快速、常速、慢速)。测试数据分2组:新型步态辅助医学诊疗系统测试数据为试验组,Vicon运动捕捉系统测试数据为对照组,比较两组步态测试数据的差异性。结果受试者在快速、常速行走中,试验组左右侧的步频、单步时间、跨步时间与对照组同名侧比较差异均无统计学意义(P>0.05),试验组左右侧的步长、步幅、步宽、步速与对照组同名侧比较差异均有统计学意义(P<0.05)。受试者在慢速行走中,试验组左右侧的步频、单步时间、跨步时间、步长、步幅、步速与对照组同名侧比较差异均无统计学意义(P>0.05),试验组左右侧的步宽与对照组同名侧比较差异均有统计学意义(P<0.05)。受试者在快速、常速、慢速行走中,试验组左右侧髋关节最大屈曲角度与对照组同名侧比较差异均无统计学意义(P>0.05),试验组左右侧髋关节最大伸展角度、膝关节最大屈曲角度、膝关节最大伸展角度、踝关节最大跖屈角度、踝关节最大背伸角度与对照组同名侧比较差异均有统计学意义(P<0.05)。受试者在常速行走,右侧为例的情况下,试验组时空参数(步频、单步时间、跨步时间、步长、步幅、步速)以及髋、膝、踝关节的最大屈曲和伸展角度与对照组同名数据具有很高相似度,变化趋势基本保持一致;两组数据基本都在文献报道的步态数据参考范围的低值与高值之间。结论新型步态辅助医学诊疗系统不依赖穿戴设备、操作简单、经济、依从性好,具有检测步态的可行性、实用性、相对准确性,值得临床逐步应用及推广。

Response of a transmission tower-line system at a canyon site to spatially varying ground motions

Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan and Wenchuan earthquake in Sichuan,China. These collapses were partially caused by the pulling forces from the transmission lines generated from out-of-phase responses of the adjacent towers owing to spatially varying earthquake ground motions. In this paper,a 3D finite element model of the transmission tower-line system is established considering the geometric nonlinearity of transmission lines. The nonlinear responses of the structural system at a canyon site are analyzed subjected to spatially varying ground motions. The spatial variations of ground motion associated with the wave passage,coherency loss,and local site effects are given. The spatially varying ground motions are simulated stochastically based on an empirical coherency loss function and a filtered Tajimi-Kanai power spectral density function. The site effect is considered by a transfer function derived from 1D wave propagation theory. Compared with structural responses calculated using the uniform ground motion and delayed excitations,numerical results indicate that seismic responses of transmission towers and power lines are amplified when considering spatially varying ground motions including site effects. Each factor of ground motion spatial variations has a significant effect on the seismic response of the structure,especially for the local site effect. Therefore,neglecting the earthquake ground motion spatial variations may lead to a substantial underestimation of the response of transmission tower-line system during strong earthquakes. Each effect of ground motion spatial variations should be incorporated in seismic analysis of the structural system.

初探光学空间定位虚实交互表演环境系统的设计

针对演艺领域提出一种基于光学空间定位虚实交互表演环境系统的实施方案,解析了设计思路、系统架构、技术路线,并针对实施难点提出了解决方案。

一类不确定运动系统的空间迭代学习控制

本文讨论了一类在有限空间区间内重复运行的不确定运动系统的跟踪控制问题.通过引入空间状态微分算子和空间复合能量函数,提出了一种空间周期的自适应迭代学习控制算法.首先利用空间状态微分算子,将系统从时间域转化到空间域形式.然后基于空间复合能量函数设计了控制器,利用含限幅作用的参数自适应律逼近系统中的不确定性,同时引入鲁棒项共同抑制非参数不确定性的影响.通过严格的数学分析,证明了在标准初始条件和随机有界初始误差两种情况下的跟踪误差收敛性.最后通过列车仿真进一步验证了该算法的有效性.

基于WebGIS的强震动台网数据发布系统研究

WebGIS技术在美、日等国家强震动台网发布系统中得到了广泛应用,本文提出了我国强震动台网系统利用WebGIS发布信息的设计思路。对系统环境设计和关键技术以及空间数据库架构进行了研究,指出分布式WebGIS的应用研究已成为强震动台网数据发布系统建设的发展趋势。

一类非参数不确定运动系统的自适应空间重复学习控制

针对一类在空间区间内重复运行的非参数不确定运动系统,本文提出一种基于李雅普诺夫方法的自适应空间重复学习控制(SRLC)策略。首先,引入空间微分算子将系统从时间域转换到空间域形式,并将系统非参数不确定性划分为空间周期不确定和非周期不确定两部分。其次,设计全饱和空间重复学习律估计和补偿空间周期非参数不确定部分,同时保证被估计值的连续性和有界性。此外,将非周期不确定部分转换为参数化不确定形式,并设计其上界参数的空间自适应更新律用以补偿系统非周期不确定。最后,设计控制器确保系统输出能够精确跟踪空间周期性期望信号。仿真结果验证了所提方法的有效性。

微系统领域的关键技术

评述微系统的 3维成形、空间运动机构制作和微作业技术。提出了微系统的定义 ,指出了它区别于宏系统、微电子系统的特点及这些特点对上述 3个技术的影响。评述了 L IGA、DRIE、EDM、微浮雕、折叠法、RPM 6种 3维成形法 ,并指出如何组合它们以适应微光学系统、微流体系统、微机构等商品化的配套需要。评述了微运动副的制造方法、带弹性变形件及柔性变形件的微机构设计原理和制造方法 ,并对它们的选择原则提出建议。评述了微物体在流体中的作业、微注射、狭窄空间中的作业、工作台—机器人系统上的微作业。提出了值得研究的若干课题群。

仿复眼的动目标位置快速估计算法

昆虫复眼由成百上千个小眼组成,具有大视范围内的快速识别能力.本文仿昆虫复眼的快速定位特性,提出一种基于小眼视场交汇空间分区的动目标位置快速估计法.根据探测器阵列组合与空间视野范围的对应关系建立参量方程,参量为检测到动目标时探测器阵列的组合方式;模拟探测器阵列与运动目标,验证定位算法的快速估计能力;最后通过阈值比较获得检测到目标的探测器组合方式,求解参量方程实现目标定位.对定位计算结果与实际模拟距离进行比较,结果表明该算法能够实现不同大小目标在不同运动轨迹下的位置估计.

五相混合式步进电动机在空间扫描驱动机构中的应用

介绍了采用步进电动机、谐波减速器和绝对式编码器构成的扫描镜驱动机构进行成像光谱仪运动补偿的方案。说明了选用五相混合式步进电动机的合理性,研究了五相混合式步进电动机在该应用中的特殊要求,驱动技术和控制实现方法。首先,指出了扫描镜和相应驱动方案对步进电动机的特殊要求。接着,针对扫描镜低速运动补偿和高速运行回归初始位置两种工况,提出了一种基于隔相五边形绕组联结方式的新型驱动方法,即调频调压结合恒频变脉宽调制(PWM)的方法,重点分析了该驱动方式对扫描机构运行性能的影响。最后,利用相关测试设备和相应方法对扫描镜的运行精度进行了实验测量。结果表明:扫描镜在以0.1～0.5(°)/s低速进行匀速运行和跟踪给定运动补偿曲线运行两种情况下,角速度的均方根误差均<5.5%,基本满足一般成像光谱仪对扫描机构的工程应用要求。

基于数控指令修正的数控内圆磨床几何误差补偿

为减小各几何误差对机床加工精度的影响、提高机床加工精度,以数控精密内圆磨床为研究对象,基于多体系统理论及齐次坐标变换原理,得到磨床的空间运动误差模型,建立几何误差与运动位置之间的映射关系。对加工补偿点的确定方法及数控指令修改方法进行研究,得到精密加工数控指令;通过软件进行阶梯轴试件的加工仿真验证,分别得到补偿前后的数控指令,并选取5个补偿点;补偿前后到理想位置的空间误差分别从0.616、0.607、0.614、0.295、0.376 cm减小到0.354、0.398、0.376、0.188、0.255 cm,分别减小42.5%、34.4%、38.6%、36.3%、32.1%。结果表明:通过修改数控指令能够提高机床加工精度。

地震动空间变化对高压输电塔线体系地震反应的影响

通过数值模拟研究了地震动空间变化对高压输电塔线体系地震反应的影响。建立了输电塔线耦联体系三维有限元模型,考虑了输电线的几何非线性特征;在考虑地震动的行波效应、部分相干效应和局部场地效应以及多维性基础上,依据功率谱密度函数、相干函数和《电力设施抗震设计规范》模拟了空间变化地震动时程;分别研究了地震动空间变化的行波效应、部分相干效应和局部场地效应对输电塔线体系地震反应的影响。研究结果表明,地震动空间变化对输电塔线体系地震反应影响显著,忽略这些因素将会低估结构的反应。因此对于输电线路实际工程的抗震设计,需要考虑地震动空间变化效应的影响。

现代汉语中“起”的句法语义系统新解:事件表达与时空转换

现代汉语中,趋向动词“起”可以独立做谓语,做动后补语,做动前成分。做动前成分时,“起”既是词内成分,又承担句法功能。“起”族词汇是一个个位移事件的凝固,能挖掘更多“起”的句法语义特征。汉语的“起”作为语素能实现从语素到词、短语、句子的三级跨越,直接参与到句法配置中,四个层面一步到位。“位移事件表达”和“时空转换”以及汉语词法、句法配置的“贯通性”原理是“起”的句法语义系统的内在制约因素。

WebGIS在强震动台网发布系统中的应用

WebGIS技术在美、日等国家强震动台网发布系统中得到了广泛应用。本文提出我国强震动台网系统利用WebGIS发布信息的设计思路。对系统环境(硬件和软件)设计和关键技术以及空间数据库架构进行研究。指出分布式WebGIS的应用研究已成为强震动台网发布系统建设的发展趋势。

基于人体行为模型的跌倒行为检测方法

随着移动互联网的广泛应用,智慧社区等一系列移动互联应用等得到人们的重视,特别是以居家养老的老年人防跌倒检测备受关注.针对目前老年人跌倒没有及时得到检测报警,从而无法及时救助,进而产生更严重的安全性的问题,本文提出了一种跌倒检测方法.本文提出的方法首先对特定人体进行扫描,利用人体建模工具poser构建出人体模型,在运动过程中根据关节点位置将二维坐标映射出相应的三维坐标并通过节点位置预测算法对映射后的三维坐标进行关节点位置预测,然后将预测后的子关节聚合到父类三维空间坐标轴中并预测出父类关节点的运动状态,当子关节点与父关节点预测结果同时处于跌倒状态,则判断人体所处于跌倒状态.由于所建立的运动模型在运动特征上具有较高的真实性,以此获取关节点的数据变化真实可靠.经过大量的实验数据表明,本文提出的跌倒检测方法可以精准实时反应运动状态,检测准确率为99%,由此可见本文提出的方法应用于跌倒检测是有效并可靠的.

基于意象图式的动词“入”的多义体系及意义连接机制探究

空间关系是人类认知的重要基础,由此而形成的意象图式对空间运动词的语义体系具有直接的驱动作用。本文利用意象图式理论,分析空间运动动词"入"的多义体系及意义连接机制。分析表明,动词"入"的中心义位随着语义角色的空间相对位置关系、运动路径和方式的变化不断延展,形成一个相互连接的辐射网络。该网络以空间意象图式为纲,以转喻和隐喻为目,立体连接。从认知的角度阐释多义义项之间的连接和演变机制,有助于系统构建汉语动词语义模型,对汉语教学实践具有重要意义。