基于频域搜索的梳状谱信号检测方法

由于梳状谱信号多普勒容限较小,利用常规的匹配/相关检测方法进行检测时,需要较大数量的拷贝信号与计算量。针对这一问题,本文提出一种基于频域搜索的梳状谱信号检测算法。通过利用梳状谱信号频域多峰结构的特点,根据信号的先验信息计算出不同径向速度下回波信号的频点分布,对接收的信号在频域进行搜索累计的方法同时实现信号的检测与速度估计。仿真分析证明了本文算法的有效性。     

基于AQWA的双浮箱-双水平板浮式防波堤水动力分析

运用AQWA软件,针对双浮箱-双水平板浮式防波堤,建立不规则波作用下浮体锚链的耦合模型,研究时域情况下,改变水平板与浮箱的垂直间距,分析浮体运动响应以及锚链受力情况;并深入探讨了不同波浪周期和波高情况下水平板长度对浮体运动响应以及锚链受力的影响.结果表明,增加水平板与浮箱的垂直间距和水平板长度,可以有效减小浮体运动响应和锚链受力.波高和波浪周期是浮体重要的水动力因素,波高越大,波浪周期越长,浮体运动响应越剧烈;当浮体水平板长度达到21米左右时,整个防波堤达到最佳锚泊状态.     

基于船舶领域和MMG的最晚施舵点/CRI研究

提出了一种基于MMG和船舶领域的LSP计算模型,以及改进的空间碰撞危险度（space collision risk index,SCRI）/时间碰撞危险度（time collision risk index,TCRI）模型,并进行了计算机仿真.结果表明：水动力模型精度可满足研究与实践要求;基于二分法的LSP模型能快速、可靠收敛;LSP和SCRI/TCRI模型更符合海员通常做法和避碰规则的公认理解.     

动载下沥青路面超孔隙水压力分析

沥青路面结构内部的孔隙水在高速行车荷载的作用下形成的瞬时超孔隙水压力是造成路面水损害的重要原因。文中采用Hankel变换和波数域离散方法求解弹性饱和半空间体系的动力响应问题。分析了沥青路面在饱水状态下其内部孔隙水压力的变化规律以及弹性模量等材料参数变化时对孔隙水压力的影响。     

冷铣刨机金属探测技术研究

随着冷铣刨机在路面养护施工中的大量使用,铣刨机金属探测技术的应用显得越来越重要。介绍了金属探测技术方法的选择和金属探测器的应用情况,并通过实验确定了金属探测器安装在铣刨机上的最佳数量、位置和高度。     

Transient responses of a VLFS during landing and take-off of an airplane

The transient elastic deformation of a pontoon-type very large floating structure (VLFS) caused by the landing and take-off of an airplane is computed by the time-domain mode-expansion method. The memory effects in hydrodynamic forces are taken into account, and great care is paid to numerical accuracy in evaluating all the coefficients appearing in the simultaneous differential equations for the elastic motion of a VLFS. The time-histories of the imparted force and the position and velocity of an airplane during landing and take-off are modeled with data from a Boeing 747-400 jumbo jet. Simulation results are shown of 3-D structural waves on a VLFS and the associated unsteady drag force on an airplane, which is of engineering importance, particularly during take-off. The results for landing show that the airplane moves faster than the structural waves generated in the early stage, and the waves overtake the airplane as its speed decreases to zero. The results for take-off are essentially the same as those for landing, except that the structural waves develop slowly in the early stage, and no obstacle exists on the runway after the take-off of airplane. The additional drag force on an airplane due to the elastic responses of the runway considered in this work was found to be small in magnitude.     

衬砌脱空雷达波数值模拟与定量解释

地质雷达是隧道衬砌脱空病害检测主要方法,常规探测理论是以菲涅尔带半径为最终空间分辨率,小于该半径的脱空不能识别,而大于该半径的脱空在定量解释上也存在困难。针对隧道脱空检测常用900 MHz天线,采用时域有限差分对不同脱空量的模型进行雷达波数字模拟计算,并合成雷达记录剖面。在分析脱空区域顶、底反射叠加波形特征及振幅变化的基础上,给出不同脱空量模型的波形双峰极值点幅度变化规律,提出基于极值点振幅比反演脱空量的解释策略,并给出反演结果的拟合算法。该策略不仅为脱空区脱空量分析提供一条途经,同时为地质雷达在脱空定量解释方面提供有效的技术手段。     

一种基于乘性规则和支持向量域的水中目标识别分类器探讨

目标识别是水中设备智能化的关键技术之一.通过阐述支持向量域描述(SVDD)以及乘性规则(GA)的原理,提出基于乘性规则和支持向量域结合的方法对水中目标进行分类识别,对比SVM算法需要支持向量数多,运算速度慢的缺点,该方法能有效提高优化识别速度.     

Parameters optimisation of a vehicle suspension system using a particle swarm optimisation algorithm

The purpose of this paper is to determine the lumped suspension parameters that minimise a multi-objective function in a vehicle model under different standard PSD road profiles. This optimisation tries to meet the rms vertical acceleration weighted limits for human sensitivity curves from ISO 2631 [ISO-2631: guide for evaluation of human exposure to whole-body vibration. Europe; 1997] at the driver's seat, the road holding capability and the suspension working space. The vehicle is modelled in the frequency domain using eight degrees of freedom under a random road profile. The particle swarm optimisation and sequential quadratic programming algorithms are used to obtain the suspension optimal parameters in different road profile and vehicle velocity conditions. A sensitivity analysis is performed using the obtained results and, in Class G road profile, the seat damping has the major influence on the minimisation of the multi-objective function. The influence of vehicle parameters in vibration attenuation is analysed and it is concluded that the front suspension stiffness should be less stiff than the rear ones when the driver's seat relative position is located forward the centre of gravity of the car body. Graphs and tables for the behaviour of suspension parameters related to road classes, used algorithms and velocities are presented to illustrate the results. In Class A road profile it was possible to find optimal parameters within the boundaries of the design variables that resulted in acceptable values for the comfort, road holding and suspension working space.     

南水北调东线分流区通航水流条件及改善措施

采用平面二维水流数学模型,对南水北调东线某工程调水分流区通航水流条件进行了计算分析,提出了改善通航水流条件的方案.计算结果表明,现状条件下分流区通航水流条件不能满足规范要求,方案2通过扩挖金宝河及分流区南侧对回流区和横向流速的改善效果较好,推荐其作为工程改善措施.