近似模型在非均匀环肋圆柱耐压壳优化中的应用研究

为提高潜水器耐压壳的稳定性和材料的利用率,该文在圆柱耐压壳设计中引入了非均匀肋骨布置方案,采用不等刚度不等间距分布的肋骨形式。在优化过程中,引入了近似模型技术,提出基于近似模型的非均匀环肋圆柱壳结构优化设计方法,通过试验设计在设计空间内选取样本点,建立近似模型,并以此搭建了近似模型优化策略对环肋圆柱耐压壳进行优化。研究结果表明,对于非均匀环肋圆柱壳采用合理的肋骨布置方案能有效地提高其力学性能及材料利用率;二阶 RSM 近似模型和 RBF 近似模型均能合理反映样本空间的样本点,基于近似模型优化方法能以较小的计算量克服优化过程中出现的数值噪声和错误。良好的优化结果表明该优化方法具有广泛的应用前景和空间。     

基于不确定需求的电动汽车共享系统规划方法

电动汽车共享有助于解决交通拥堵和环境污染问题。为提高电动汽车共享系统效率，保 障系统的可持续性，本文考虑共享需求的不确定性，提出单向电动汽车共享系统最优配置方法。 首先，以多情景处理共享需求的不确定性，以车站和状态集计车辆和调度员，考虑需求价格弹性， 构建共享电动汽车系统配置模型。然后，针对3类共享出行需求价格弹性函数，根据需求为整数 的特点，设计基于割线的外逼策略，提出用于模型求解的外点法。最后，算例证实了考虑共享需 求不确定性的必要性，分析了共享需求方差、弹性以及需求量对共享电动汽车系统利润的影响。 研究结果表明，共享电动汽车系统利润随需求量和需求方差的增加而增加，随需求弹性绝对值的 增加而减少。     

Quadratic approximation and convergence of some bush-based algorithms for the traffic assignment problem

This paper first shows that LUCE (Gentile, 2012), a recent addition to the family of bush-based algorithms, is closely related to OBA (Bar-Gera, 2002). LUCE’s promise comes mainly from its use of the greedy method for solving the quadratic approximation of node-based subproblems, which determines the search direction. While the greedy algorithm accelerates the solution of the subproblems and reduces the cost of line search, it unexpectedly disrupts the overall convergence performance in our experiments, which consistently show that LUCE failed to converge beyond certain threshold of relative gap. Our analysis suggests that the root cause to this interesting behavior is the inaccurate quadratic approximation constructed on faulty information of second-order derivatives. Because the quadratic approximations themselves are inaccurate, the search directions generated from them are sub-optimal. Unlike OBA, however, LUCE does not have a mechanism to correct these search directions through line search, which explains why its convergence performance suffers the observed breakdowns. We also attempt to improve LUCE using the ideas that have been experimented for the improvement of OBA. While these improvements do work, their effects are not enough to counteract the inability to adjust sub-optimal search directions. Importantly, the fact that the search direction has to be corrected in line search to ensure smooth convergence attests to the limitation of origin-based flow aggregation shared by both OBA and LUCE. These findings offer guidelines for the design of high performance traffic assignment algorithms.     

一种多学科设计优化近似模型构建方法

通过采用单个参数控制样本的误差界限、采用Laplace损失函数和改变置信区间项,给出了一种基于单参数的Lagrangian支持向量回归算法。以实际数值函数为例,通过采用三组不同样本集进行拟合训练,构建了基于支持向量机的近似模型;以石油平台支援船总阻力估算为例,通过与模型试验及其他典型方法的对比,检验了算法用于近似模型构建的准确性和适用性。研究结果表明,采用支持向量机方法构建近似模型在小样本条件下比神经网络等传统方法具有更好的泛化性和推广能力,能够有效提高计算精度与优化效率,在复杂系统多学科优化设计中具有很大的应用价值。     

贴近度对模糊诊断矩阵的实时修正应用研究

能否正确地建立故障征兆与故障原因之间的从属关系直接决定了模糊逻辑诊断的成功与否，诊断矩阵中各个元素的取值与实际情况的符合程度直接影响到故障诊断的准确性。因此，在确立隶属函数之后，诊断矩阵与实际情况的符合程度是准确模糊诊断的关键。提出了利用贴近度，实时加权修正诊断矩阵的方法。     

平坦海底界面上圆形平板的高频回声特性

用物理声学方法(Kirchhoff近似)结合镜像原理给出了计算界面附近目标声反射的方法.研究了泥砂类沉积物构成的平坦海底界面上不同倾斜角度的刚性圆形平板某一面在不同入射掠射角的高频回声特性.计算中考虑了圆形平板在某些倾斜角度存在的遮挡影响.结果表明,圆形平板垂直于海底界面时,在大部分掠射角范围内的目标强度最大.若要减小回波强度,则圆形平板应倾斜放置.     

深水波频域格林函数及其高阶导数算法研究

文章研究了无限水深自由面格林函数一种新的算法,该算法将计算域重新划分为五个子区域,在每一个子区域内只涉及级数展开,没有使用插值表及数值积分,与现有格林函数算法相比,不仅给出一阶导数值,而且能高效地计算二阶导数,这在格林函数微分方程求解及高阶面元法中非常有用.数值结果表明,该方法计算速度快且一阶导数和二阶导数的计算精度达到10-9.     

基于近似模型的海上发射船船型优化

基于耐径向基函数神经网络模型(RBF),以火箭承受弯矩为单目标优化函数,对双体发射船船型参数进行优化研究。选定对船型参数CB和L/B作为优化变量,利用Lackenby方法,对船型参数化建模,应用最优拉丁超立方方法(LHD)选取样本点,采用二次插值方法扩充样本点数据,建立双体船运动响应及阻力近似模型,利用多岛遗传算法(MIGA)搜索最优船型。结果表明优化后船型的火箭弯矩减小3.86%,从而为双体火箭发射船的设计及相关船型研究提供参考。     

考虑水弹性影响的螺旋桨设计方法研究

船用螺旋桨工作在低速重负荷工况、或采用大侧斜几何型式或采用复合材料时,其流固耦合现象较为突出,螺旋桨设计中若无法准确考虑其间的水弹性影响,将会造成船机桨失配及实船推进性能的错误预报。文章基于螺旋桨环流理论设计方法、螺旋桨流固耦合算法以及逐步逼近法,形成了一套可考虑水弹性影响的螺旋桨设计方法,重点讨论了流固耦合中水动力载荷更新方式、逐步逼近法中预变形松弛因子的选择对设计结果的影响。通过大侧斜螺旋桨及复合材料螺旋桨设计实例,进一步阐述了在螺旋桨设计中考虑水弹性的必要性,也验证了所开发设计平台的有效性。该设计平台为后续复合材料螺旋桨的优化设计提供了基础。     

Stability enhancement of a high-speed train bogie using active mass inertial actuators

In this study, a method regarding frame lateral vibration control based on the state feedback of an additional oscillator is proposed, so as to improve the bogie hunting stability. The multi-objective optimisation method (MOOP), with two objective functions of the stability index and control effort, is solved by the NSGA-II algorithm to obtain the feedback gains. The frame lateral vibration control can effectively improve the bogie hunting stability according to the linear and non-linear analysis of a high-speed train bogie, in which a fault of the yaw damper and time delay in the control system are considered. The effect of the oscillator suspension parameters and time delay on the system stability and robustness are analysed. The results show that the damped vibration frequency of the oscillator should be equal to the bogie hunting frequency, but a harder oscillator suspension can be used to improve the hunting critical speed margin of the bogie control system. However, just as how the feeding the frame states back directly, a hard oscillator suspension will lead to instability in the control system at a certain time delay. Therefore, the improvement of bogie hunting stability and reduction of control system stability must be considered when optimising the oscillator parameters. For the 350?km/h train bogie covered in this study, the optimal mass, natural frequency and damping ratio of the additional oscillator are acquired.