Experimental Investigation of the Effect of Bow Profiles on Resistance of an Underwater Vehicle in Free Surface Motion

In this paper, towing tank experiments are conducted to study the behavior of flow on a model of the underwater vehicle with various shapes of bows, i.e. tango and standard bows in free surface motion ...     

内燃机活塞环表面处理技术的发展趋势

阐述了现代内燃机活塞环表面处理技术的发展趋势,并据此提出了建议。     

汽油机燃烧室紧凑性评价参数分析

对燃烧室紧凑性评价参数面容比A/V值进行了分析,讨论了其局限性。提出了新的内燃机燃烧室紧凑性的衡量方法,即面面比S/A,在等容积条件下,进行了各种燃烧室紧凑性及火焰传播距离的比较。     

面元法预估导管螺旋桨水动力性能的一种新方法

采用一种新的方法预估导管螺旋桨的水动力性能;导管和螺旋桨均采用基于速度势的面元法,它们间的影响通过相互的诱导速度势数值迭代来体现．与诱导速度体现相互影响的方法相比,本文方法可节省编程及计算时间;对JD系列导管螺旋桨的计算与实验结果的比较表明,该方法可以有效地预估导管螺旋桨的水动力性能．     

低表面处理涂料在港口机械上的应用

在介绍了目前国内通用的港口机械防腐涂料的基础上,针对传统防腐涂料存在的问题,阐述了未来防腐涂料的发展趋势。着重介绍了一种新型的低表面处理特种改性环氧涂料,具有生态环保,无毒阻燃,超强附着力,高边棱保持率。     

浅埋暗挖隧道下穿结构物的施工沉降分析

以北京地铁奥运支线起点(熊猫环岛站)区间隧道下穿健安桥的设计与施工为背景,分析浅埋暗挖隧道穿越地面结构物施工如何有效地控制沉降,探讨施工时应注意的关键环节和采取的措施,以此作为今后类似工程施工的依据和借鉴.     

路面铣刨刀具失效机理与形式分析

对路面铣刨刀具结构组成、切削时象、工作状态和失效机理的进行了简洁的论述。着重分析了刀具正常失效和非正常失效产生的原因．提出了保证刀具正常失效的措施。     

浅埋暗挖地铁隧道施工监测方法

文章以重庆市地铁一号线大坪车站临时施工便道为例,对在浅埋、软岩条件下既有隧道拆除采用工字钢支顶、风镐破岩,新建隧道采用台阶法环形开挖预留核心土、人工非爆破开挖的施工方法,通过现场监控量测,得出最大地表沉降仅为3.82mm,表明采用合理的施工方法可以减少地表沉降。     

含软弱土层边坡稳定性分析的全局滑面自动搜索技术

提出了一种用于边坡稳定性分析的全局滑面自动搜索技术,首先采用三角网格进行了边坡土层的几何离散,然后,结合蒙特卡洛法等角/等边逐段扫描与模拟退火法,构建了全套的边坡全局临界滑面搜索扫描算法。以Fortran和Matlab为计算手段进行联合编程,采用简明Morgenstern-Price法进行了边坡稳定性分析计算。通过选用3个算例进行了算法的可靠性验证,计算结果表明:截面三角网格划分方法具有良好的适应性,能较好地对不规则层位几何形状进行离散;多段折线滑面具有较圆弧滑面更为优秀的极限滑面定位功能,其安全系数随着滑面段数的增加会逐步达到收敛;本搜索方法可不依赖于工程师经验进行多段折线初始滑面的大致范围选择,其能快速地、全自动地进行由弱到强不同复杂土质情况的边坡稳定性计算分析,并能找到全局临界滑面与安全系数。     

Sea state estimation based on vessel motion responses: Improved smoothness and robustness using Bézier surface and L1 optimization

Floating structures oscillate in waves, where these wave-induced motions may be critical for various marine operations. An important consideration is thereby given to the sea states at the planning and operating stages for an offshore project. The most important information extracted from a sea state is the directional wave spectrum, indicating wave direction, significant wave height, and wave spectrum peak period. Among several available methods of measuring and estimating the directional wave spectrum, the wave buoy analogy technique based on vessel motion responses is an in situ and almost real-time solution without extra costs of devices. If the forms of the wave spectra are not predefined in the estimation, the method is called a nonparametric approach. Its most remarkable advantage is the flexible form, but the smoothness should be regulated. After the discrete Fourier transform has been applied to the measured vessel motions, smoothing is necessary. However, this process results in disturbed vessel cross-spectra and a lowpass characteristic of the windowing function. This paper presents a nonparametric approach for directional wave spectrum estimation based on vessel motion responses. It introduces novel smoothness constraints using Bézier surface and includes a more robust estimate using L1 optimization. Both techniques are applied to the wave buoy analogy for the first time. Numerical simulations are conducted to verify the proposed algorithm.