基于快速行进法地震层析成像研究

地震层析成像是通过对观测到的地震波运动学特征(射线路径、走时)和动力学特征(振幅、相位、频率)的资料进行分析,反演得到地下地质体结构、速度分布等信息的一种地球物理方法。由于快速行进法具有无条件稳定、精度高、适应能力强等优点,所以被广泛应用于地震层析成像领域。本文将二维快速行进法应用于地震层析成像的研究中,完成了均匀介质情况下的入射波和反射波走时场及射线路径模拟,结果表明基于快速行进法在二维速度随深度线性变化及横向各向异性的模型正演中取得了理想的效果。     

基于BIM和元胞自动机的建筑#br# 火灾救援路径动态规划研究

建筑物发生火灾时,建筑物复杂的内部环境以及火灾的实时蔓延会给参与室内救援工作的消防员带来隐患甚至生命危险。为提高消防员建筑火灾室内救援效率,文章提出了基于BIM技术和元胞自动机的消防员救援路径动态规划系统。该系统中,创新性将BIM建筑模型与元胞自动机有机结合,建立了一种新型元胞自动机路径规划智慧模型,该模型利用场景分层和碰撞检测的方法自动识别建筑物的各种构件和内部环境,具有很高的智能性和普适性;在火场中添加动态障碍物模型和随机灾变火模型,并利用实时检测方法研究真实火场的动态性对消防员救援路径的实时影响,使消防员科学、高效地避开静态、动态障碍物并安全完成救援。使用该系统对一座单层大空间体育馆进行实例模拟,验证了该系统的适用性,为制定建筑火灾消防救援策略、实现高效精准救援以及智慧消防提供技术支持。     

复杂型腔环切拐角过渡刀轨生成技术

针对环切刀轨中存在的拐角及残区问题,提出采用三段式Clothiod曲线光滑拼接的方法进行过渡优化。首先,借鉴骨架线提取的原理判断拐角残区并提取出残区步长;然后,在残区步长的基础上,选取过渡控制点和初始插入点作为曲线过渡的特征点;最后,在特征点的约束下,将曲线和直线进行过渡连接,并保证过渡曲线的C2阶连续。仿真加工测试结果表明,该方法能有效切除环切拐角残余并实现刀轨的平稳过渡,同时能很好地缩短加工时间和提高整体的加工质量。     

基于 EON studio的马铃薯覆膜机的虚拟装配技术研究

通过计算机仿真,将之前只有在物理样机试验阶段才能得到的数据通过虚拟仿真获得,以缩短设计周期和试验所需的高额费用。基于EON studio对马铃薯覆膜机的装配仿真,对其装配层次表达方法,装配序列和路径规划进行了研究,以达到对装配工艺优化的目的。     

基于SolidWorks Motion运动仿真跟踪路径的应用

通过SolidWorks Motion运动仿真工具对未定义凸轮机构从动件进行基于“时间/位移”系列数据点运动的反向驱动操作,生成跟踪路径,最终生成盘形凸轮轮廓曲线。并对新生成的凸轮机构进行实际运动仿真,验证了凸轮模型的准确性。     

Generalized selection combining with double threshold and performance analysis

In this paper, we propose a new diversity combining scheme to save power, which is called as the generalized selection combining with double threshold (DT‐GSC). It selects the branch whose SNR is above an input threshold to combine, and this process will keep running until the combined output SNR is larger than an output threshold or until all paths are examined. The values of both thresholds are required to be predetermined on the basis of the practical communication conditions. For comparing the complexity of various combining schemes, we will show the mathematical formulas of the average number of path estimation and the average number of combined branches. Moreover, we will also compare the average bit‐error‐ratio performance of the proposed DT‐GSC with absolute threshold GSC (AT‐GSC) and output threshold MRC (OT‐MRC). Numerical examples and simulation results show that the proposed DT‐GSC leads to a lower complexity than the conventional AT‐GSC and OT‐MRC while it has a satisfactory performance.Copyright © 2012 John Wiley & Sons, Ltd.     

End‐to‐end performance of transmit antenna selection and generalized selection combining in dual‐hop amplify‐and‐forward relay network in the presence of feedback errors

In this paper, end‐to‐end performance of transmit antenna selection (TAS) and generalized selection combining (GSC) is studied in a dual‐hop amplify‐and‐forward relay network over flat Rayleigh fading channels. In the system, source and destination equipped with multiple antennas, communicate by the help of single relay equipped with single antenna. Source‐destination link is not available. TAS is used for transmission at the source, and GSC is used for reception at the destination. By considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed‐form outage probability, moment generating function and moments of end‐to‐end signal‐to‐noise ratio, and closed‐form symbol error probability (SEP) expressions for channel state information (CSI)‐based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI‐based and fixed relay gains by deriving asymptotical outage probability and SEP expressions. The analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

一类高维Cantor型集合的Hausdorff维数

本文利用有关集合直积的Hausdorff维数与Hausdorff密度关系的理论,得到了一类高维Cantor型集合的Hausdorff维数,由此可构造出具有任意给定的Hausdorff维数的集合。     

A genetic algorithm with local search using activity list characteristics for solving resource‐constrained project scheduling problem with multiple modes

In this paper, we aim to solve the problem of resource‐constrained project scheduling with multiple modes (rc‐PSP/mM), in which multiple execution modes are available for each of the project's activity and with minimization of makespan as objective. We present a new genetic algorithm approach in order to solve this problem. In this procedure, we propose a new mutation operator that exploits a critical path and two new local search procedures, i.e. critical path improvement local search (cpiLS) and iterative forward/backward local search (ifbLS), using activity list characteristics. The cpiLS reduces the critical path and the ifbLS improves resource allocation of the schedule of rc‐PSP/mM. Also, to evaluate the proposed approach, we compare the results of the computational experiment on certain standard project instances with the several competing heuristic procedures presented in the literature, and it has been revealed that our procedure is one of the most competitive among the algorithms. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于改进粒子群的焊点检测路径规划方法

针对电路板的焊点检测路径优化问题,提出一种改进的粒子群优化算法。在粒子进化过程中,根据时间函数的变化,调整粒子进化参数组合。在焊点空间路径规划过程中,将最小时间函数作为移动准则。在当前焊点检测点,建立路径规划时间函数,利用改进粒子群算法求取时间函数最小点,作为下一路径点,从而逐步得到焊点移动路径。仿真结果表明,利用所提方法可以规划出一条有效最优路径,进行完成焊点路径规划任务。同时实验结果表明,相对于其他粒子群算法,该算法具有较好的收敛精度,且收敛速度可控。