Equivalent stochastic linearization for nonlinear uncertain structure under stationary Gaussian stochastic excitation

Equivalent stochastic linearization （ESL） for nonlinear uncertain structure under stationary stochastic excitation is presented. There are two parts of difference between the original system and equivalent system： one is caused by the difference between the means of original and equivalent stochastic structure; and another is caused by the difference between the original and equivalent stochastic structure which has the relation with stochastic variables. Statistical characteristics of equivalent stochastic structure can be obtained in accordance with mean square criterion, so nonlinear stochastic structure is transformed into linear stochastic structure. In order to attain that objective, the compound response spectrum of linear stochastic structure under stationary random excitation which is used in the solution is derived in the case of the mutual independence between stochastic excitation and stochastic structure. Finally, the example shows the accuracy and validity of the proposed method.     

深海拖曳系统自稳定二级拖体姿态控制研究

以具有自主调节功能的二级拖体为例,对其姿态控制进行研究。首先,建立二级拖缆的弹簧-阻尼模型,并在此基础上建立二级深拖系统的数学模型;其次,根据该系统具有非线性和时变性等特点,设计具有参数自修正功能的模糊自适应PID控制器,以实现在不同工况下对二级拖体的姿态进行控制。仿真结果表明:未加载控制器时,海况变化对拖体姿态有显著影响,其俯仰角和横滚角均会发生大范围波动;而加载模糊自适应PID控制器后,拖体通过自主调节能够将姿态波动控制在较小范围,从而满足工作要求,验证了拖缆数学模型的正确性和所采用控制方法的可行性。     

Optimal allocation of fleet’s spare parts for system reliability

Allocation of fleet’s spare parts is rarely studied due to its complexity. However, this task is extremely important because the warship’s service level highly relies on the maintenance logistics’ level. In this study, the readiness ratio is proposed as a critical index in measuring the system’s reliability. A well-established mathematical model adopting the optimization method of spare part allocation is also introduced. The objective is to minimize the number of each spare part while satisfying the fleet’s system reliability. The fault tree analysis (FTA) is applied to analyze the system’s failure logic and stratify the units on ship. As a result, the strategy of spare part sharing can be introduced in detail. The solution algorithm is developed, and the simulation experiments to obtain the key parameters are conducted. The proposed model and algorithm are applied to an actual fleet of two warships, and results show that the method above is feasible and can be directly applied into practice.     

舰船总体可靠性通用软件包研究

本文着重探讨舰船的总体可靠性的计算问题，作者将故障树分析法和多级数值仿真相结合，编制了计算舰船总体可靠性各项参数（例如任务可靠度，战备完好率等）的软件包。在系统分析方面，作者巧妙应用多级数值仿真法，提供了计算可维修系统可靠性的新途径。并在本文最后给出了一个关于潜艇可靠性参数的计算实例。     

复合式土压平衡盾构机穿越闽江强透水砂层技术研究

地铁盾构机下穿江河段一般为风险最高段,且不同地层组合条件下的施工风险等级也不同。结合福州地铁1号线达道站—上藤站区间盾构穿越闽江的实例,系统地研究了复合式土压平衡盾构机穿越江底强透水砂层的施工工艺,包括施工方案的整体评估、施工前的设备改造和渣土改良、施工难点及其对策、辅助工法等。该施工工艺实现了复合式土压平衡盾构机穿越江底强透水砂层的突破,既保障了施工安全,又保证了施工工期。     

基于仿真的造船"中间产品"任务包评价方法

现代造船生产强调均衡连续，造船生产中“中间产品”任务包的合理性直接影响了造船生产效率的提高。对“中间产品”任务包的合理性进行了分析讨论，提出了一种基于计算机仿真技术的“中间产品”任务包评价方法，建立了船体零件加工分道作业线仿真模型，实现了对船体零件加工任务包合理性的仿真评估，结果表明该方法有效可行，可用于指导生产。     

基于CAD与CFD的穿梭艇局部船型特征分析

穿梭艇船型是一种针对恶劣航行条件下的高速船艇需求提出的,具有内倾式船首的、单体、高速、穿浪、排水型船。论文基于CAD和CFD技术,对影响穿梭艇在静水中阻力和兴波性能的首尾部若干局部船型特征进行了对比分析,揭示了不同船型特征下的穿梭艇性能特性间的差异,为以后相关船型的设计开发提供了有益的参考。     

焊缝对环肋圆柱壳振动声辐射的影响

将结构固有频率作为中间变量,研究焊接残余应力、结构固有频率和结构声辐射特性之间的关系。首先,分析焊接残余应力与结构固有频率之间的关系,并通过实验进行验证,结果显示焊接残余应力使结构固有频率发生了显著改变。然后,对固有频率—声辐射功率的灵敏度进行理论推导,并运用有限元法结合边界元法建立数值模型,计算该模型在指定范围内的固有频率—声辐射功率灵敏度,结果证明结构声辐射功率会随着固有频率的变化而发生显著变化。最后,综合分析焊接残余应力与结构声辐射之间的关系。结果表明,研究复杂结构的振动声辐射等动力学特性时,焊接残余应力是不能忽视的影响因素。     

改进型双支柱SWATH的兴波阻力研究

以一艘用于内河渡轮的双支柱小水线面双体船(SWATH)为研究对象,提出不同于传统设计的片体艏部形状,并调整前支柱位置,利用Shipflow软件对片体、支柱两者之间的兴波干扰以及船舶整体的兴波阻力进行计算和比较,得到片体艏部型线和前支柱位置对船体兴波阻力的影响,并以此为依据提出了此种船型的改进方案.     

支柱构型对斜支柱小水线面双体船在迎浪中运动响应的影响

基于三维势流理论并考虑黏性阻尼,计算某斜支柱小水线面双体船使用不同支柱构型的耐波性能,结合规则波中的运动响应以及设定海域的波浪谱得到运动有义值。分析发现该船支柱长度、支柱位置及布置双支柱的变化对垂荡和纵摇有义值有显著影响,提出斜支柱小水线面双体船的支柱构型设计对提高耐波性的重要性。