混合动力船舶模式切换过程力矩协调控制

针对混合动力船舶的模式切换过程中可能出现的扭转波动,传动轴剧烈冲击和离合器过度磨损问题,提出基于模型参考控制(MRC)的力矩协调控制策略。首先建立动力传动系统动力学模型,基于此推导出电机单独推进模式的动力学模型,并作为参考模型;然后设计MRC力矩协调控制策略。仿真结果表明,与传统的模式切换方式相比,MRC控制可改善动力中断和轴系剧烈冲击,而且显著减小离合器滑摩功。敏感性分析给出了外部干扰和执行机构噪声对控制品质的影响。     

Cyclone hazards in the Arabian sea–A numerical modelling case study of Cyclone Nilofar

Cyclones cause significant loss of life and damage to properties, ecosystems and marine facilities. To address such issues, Royal HaskoningDHV (RHDHV) has developed regional tidal hydrodynamic and wave models covering the Northern Arabian Sea. A total of 29 major cyclones were identified in the Arabian Sea since 1945. However, as less information is available on Cyclone Nilofar (2014), this paper has concentrated on this event to illustrate the use of numerical modelling to simulate waves and surge generated by cyclones. Sample results from the modelling study are presented in this paper. The methodology described in this paper for modelling cyclone waves and surges in the Arabian Sea could be applied to simulate such natural hazards at other sites around the world.     

Numerical prediction of solitary wave forces on a typical coastal bridge deck with girders

In this study, a numerical method for predicting solitary wave forces on a typical coastal bridge deck with girders is utilised in order to obtain an alternative way to assess solitary wave forces on coastal bridge decks with sufficient accuracy. Firstly, a wave model based on the solitary wave theory representing the incident wave of tsunamis is applied through a computational fluid dynamics computer program, where the shear stress transport k-ω model is adopted as the turbulent closure for the Reynolds Averaged Navier–Stokes model equations. Then, the numerical wave profiles and the predicted wave forces are compared with the analytical solutions and the reported laboratory measurements, respectively. These verifications assure the results in the following parametric study reliable. Finally, comparisons between the numerical results and those acquired through the empirical methods are conducted in order to examine the appropriateness of these empirical procedures regarding this specific case. Furthermore, an expanded formula is proposed with the definitions of the key parameters being discussed thereafter. This method can be expanded to cases where different deck cross sections rather than the typical one used in the present study are considered and to scenarios where different wave parameters are involved. It is hoped that the expanded formula could provide straightforward but advisable results for practicing engineers.     

基于地下VLF人工信号源的定位技术研究

基于甚低频电磁波(VLF)穿透地层能力,研究地层对信号造成的影响,评估频率、功率和信号穿透能力的关系;从信号源、天线、信号处理滤波等方面讨论其实现的原理及关键技术;筛选适合地下-地表单向通信的合理方式和载波机制;建立简化的磁偶子定位模型,完成信号源的定向和定深。总结甚低频定位技术的关键方案,为煤层气水平井、水平对接孔、定向钻进导向孔、矿井救援等钻探领域中孔内信号传输提供一种新的通讯技术。     

Propagation characteristics of microwaves in dusty plasmas with multi-collisions

In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic(EM) waves through uniform, unmagnetized and weakly ionized dusty plasma. The Drude model is improved to describe the dielectric property of dusty plasmas, which accounts for collisions including electron–molecule, electron–ion, and electron–dust particles. Based on the improved Drude model, the propagation characteristics of microwaves in dusty plasmas have been numerically calculated and studied.The results show that the propagation characteristics of microwaves through dusty plasmas are different from those through normal plasmas. The effects of dust density and size are mainly studied. Numerical results indicate that the momentum transfer between electrons and dust grains makes more energy loss. The dust density and dust size have a similar influence on EM wave propagation, resulting in less transmission and more absorption.     

三沙1号交通补给船主推进动力系统集成研究

从主推进动力系统方案设计、技术设计、施工设计、试验验证等方面介绍了三沙1号交通补给船主推进动力系统集成。该船主推进动力系统集成的成功应用表明:船舶动力系统集成的优势巨大,尤其对于系统复杂、技术难度高、质量要求高的高附加值船舶。     

船板钢CCT曲线的测定与分析

利用Gleeble3500热模拟试验机对船板用钢进行模拟试验,采集温度-膨胀量曲线,并结合金相法、硬度法绘制出试验材料的CCT曲线。分析CCT图和试验钢显微组织照片,得出不同冷却速度下该钢的组织转变情况。随着冷却速度的逐渐增大,试验钢的组织由多边形铁素体、准多边形铁素体逐步向粒状贝氏体、贝氏体铁素体的转变,同时显微硬度也随冷速的升高呈明显的上升趋势。     

隧道设置减震层减震机制研究

 通过Fourier-Bessel函数展开法,推导平面SV波垂直入射下半无限弹性介质中圆形双层衬砌结构、围岩–减震层–衬砌洞室的动应力集中系数级数解,分析入射波频率、减震层弹性模量和厚度对动应力集中系数的影响,并结合数值模拟分析结果对比,深入研究减震层减震机制。研究结果表明：入射频率对衬砌动应力集中系数有显著影响,减震层对低频波具有较好的减震效果;由于减震层剪切模量低,围岩和隧道可以剪切变形,从而减小了作用在衬砌外部的法向作用力,降低了衬砌内侧最大动应力集中系数,但围岩和衬砌外侧切向应力增大;随着减震层与围岩弹性模量之比减小,减震层厚度增大,二次衬砌动应力集中系数变小,减震层与围岩的弹性模量比宜低于1/10～1/20,和减震层弹性模量对应,存在一个最优的减震层厚度值。以一公路隧道为背景,开展隧道减震层结构大型振动台试验研究,结果表明：隧道衬砌设置减震层后,可以显著降低衬砌内力,减小衬砌裂缝的数量。     

Propagation of the photothermal waves in a semiconducting medium under L-S theory

The model of the equations of generalized thermoelasticity based on the Lord–Shulman theory with one relaxation time is used to study the photothermal waves in a semiconducting medium. The exact expressions for the displacement components, temperature, carrier density, and stress components are obtained using normal mode analysis. Numerically simulated results are obtained and presented graphically for silicon to depict the effect of time parameter on the different physical quantities.     

船舶-自升式海洋平台碰撞相似率研究

海洋平台作为海洋能源勘探开发的主要组成部分,是海洋油气探井、钻井、开采的主要作业基地。船舶碰撞致使平台结构损伤破坏一直是威胁海洋平台安全的主要因素之一,开展海洋平台碰撞性能研究,揭示平台结构在碰撞过程中的损伤变形机理,对提升平台安全性具有重要意义。评估平台结构耐撞性能最可靠的方法是实船碰撞试验,然而因其耗资巨大而不易开展。按一定相似关系进行比例模型试验成为现实条件下的首选。本文基于相似第二定理,运用量纲分析法推导船舶-自升式海洋平台碰撞过程中各物理量的相似关系,为平台碰撞模型试验的开展及试验参数的确定提供重要依据。结合有限元仿真技术,以平台典型的T型和K型管节点为研究对象,建立不同缩尺比下的简化碰撞模型,比较验证相似理论的可靠性。研究结果表明,缩尺模型在碰撞冲击载荷下的结构损伤变形、碰撞力和能量吸收等动态响应与实尺度模型结果一致性较好。本文研究成果可以为大型平台结构碰撞模型试验设计提供技术支撑。