Mooring tension and motion characteristics of a submerged fish reef with net in waves and currents using numerical analysis

A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system. The system included a net attached to a rigid structure suspended up from the bottom with a single, high tension mooring by fixed flotation. The analysis was performed by using a Morison equation type finite element model configured with truss elements. Input forcing parameters into the model consisted of both regular and irregular waves, with and without a steady current. Heave, surge and pitch dynamic calculations of the reef structure were made. Tension response results of the attached mooring line were also computed. Results were analyzed in both the time and frequency domain in which appropriate, linear transfer functions were calculated. The influence of the current was more evident in the tension and heave motion response data. This is most likely the result of the large buoyancy characteristics of the reef structure and the length of the mooring cable. Maximum mooring component tension was found to be 13.9 kN and occurred when the reef was subjected to irregular waves with a co-linear current of 1.0 m/s velocity. The results also showed that the system had little damping (in heave) with damped natural periods of 2.8 s. This combination of system characteristics promotes a possible resonating situation in typical open sea conditions with similar wave periods.     

Truss Spar平台在浮卸作业过程中结构强度分析

在桁架式深吃水立柱式平台(Truss Spar)运输作业的浮卸过程中,半潜驳船不断压载下潜直到Truss Spar平台自浮后拖离驳船。针对浮卸作业的双浮体状态,提出Truss Spar平台在与半潜驳船发生接触情况下的载荷计算方案并进行结构应力水平评估。基于三维势流理论及SESAM软件,考虑平台及半潜驳船双浮体之间的水动力相互影响,首先对双浮体系统进行频域下求解,得到波浪诱导载荷;然后在时域下求解波浪中双浮体的运动方程及产生的接触力;最后将这两种载荷下的结构强度分析结果进行线性叠加,得到Truss Spar平台在波浪诱导载荷及接触力联合作用下结构应力水平。对比不同波浪方向及周期下的接触力结果,研究Spar平台结构整体应力水平及高应力区域位置特点,对总体强度水平进行评估。     

光纤光栅称重传感器在大型海上浮吊中的应用

为了实现大型海上浮吊臂架结构健康状态监测,开发了大型海上浮吊光纤光栅称重传感器系统,提出了光纤光栅称重传感器设计理论,建立了传感器设计框架。通过悬臂梁理论,借助于有限元分析软件,提出了悬臂梁和受压弹性体复合结构;通过温度补偿理论与对比,提出了滤波温度补偿方案;通过迟滞效应原理,提出了双光栅式迟滞效应消除方案。进行光纤光栅称重传感器性能实验、反复性实验和稳定实验,讨论了系统的性能和可行性。并将大型海上浮吊光纤光栅实时称重系统应用于实际工程项目,成功实现了大型海上浮吊负重状况监测。     

Design and functions of floating architecture – a review

Abstract

Floating facilities such as, floating islands, floating houses, industries and, entire cities are constructions for habitation, entertainment, industrial or commercial purposes, and infrastructures are built to float on fresh- or seawater. They can be floating on air-filled or light materials. Recent developments in the ocean show a trend of offshore constructions, which can be situated above deeper waters, further offshore. These can replace the development of reclaimed lands close to shore. Floating architecture provides certain advantages for the planning of sustainable design, such as: (a) a number of viable responses to the problem of rising sea level, (b) much-needed space replacing the lack of land for agriculture, for housing, and for commercial growth, (c) the creation of new and innovative tourist destinations, (d) a much smaller ecological footprint than land-based constructions, (e) the extension of city centers that are built near the coast; (f) the possibility of green planning at an unclaimed plot. We present here a review of existing floating architecture with different functions, from housing, entertainment, and food production to industrial purposes such as wind parks and desalinization plants.     

克希霍夫叠前深度偏移在川东地区的应用

常规叠前深度偏移方法都是将数据延拓到最终面,然后从固定面偏移.在川东复杂山区,地形起伏大,地表切割剧烈,表层结构复杂,地腹构造褶皱剧烈,逆冲断层发育,地震波传播纵横向变化大,如果把数据校正到固定面来偏移,势必带来很大误差,严重影响射线追踪的准确性.另外由于该地区勘探程度较低,钻井资料很少,失去了建立偏移速度场的重要约束条件.为此针对该地区,本文提出了一种利用时间域资料约束的多模式速度-深度模型建立及分析技术,并应用基于浮动地表的Kirchhoff叠前深度偏移技术对川东某工区实际地震资料进行了处理.在该工区的应用表明,这两种技术很好解决了起伏地表的问题,对复杂地质体有较强的适应性,并且在有限钻井资料情况下,也能快速高效建立精确偏移速度场.最终偏移后的结果跟叠后时间偏移处理的结果相比归位精度得到显著提高,断层断点更为清楚,而且过井深度偏移剖面与钻井深度对比吻合也比较好,在井深度对比中各层误差均小于50 m,各层深度误差小于1%,为后续的地质研究提供了很好的资料.     

基于六普数据的中国流动人口住房状况的空间格局

住房是流动人口融入城市、实现市民化过程中必须解决的关键问题。基于2010 年第六次人口普查数据,采用住房拥有率、租住房率、住房面积指数、住房不受干扰指数、住房质量指数和住房费用指数6 个指标考察流动人口的住房状况,并综合运用数理统计、空间自相关和系统聚类法揭示流动人口住房状况的属性特征、空间分布与集聚类型。研究发现,与城镇常住人口相比,流动人口的住房状况较差。从空间分布看,流动人口住房状况的各项指标具有显著的空间正相关,在空间分布上不仅存在集聚现象,而且有明显的集聚中心。研究结果还表明,流动人口住房条件综合状况可划分为较好、中等、中等偏下、较差4 级类型区,在全国尺度上的空间分布除个别类型外具有团块聚合的结构特征。在考虑社会公平的前提下,应分类解决不同类型区域流动人口的住房问题。     

浮船坞标校的一种新方法

针对浮船坞标校的特点,提出了利用动态 GPS进行标校的新方法.该方法可连续获取被试设备位置信息,从中挑取与被试设备自身测量同历元的 GPS数据进行方位标数据解算,然后与设备测得的数据进行比对,可有效提高浮船坞标校精度.从而解决了动态标校的实时性、一致性和准确性问题,在实际应用中取得较好效果.     

基于2 SFCA 和 Model Builder 的城市餐饮服务业可达性建模分析

城市餐饮服务业是第三产业的重要支柱。合理地分析城市餐饮服务业在空间上的可达性是合理规划产业布局的重要前提,也是商家选址的重要依据。本文采用两步移动搜索分析法（2SFCA）,基于Python语言和ArcGIS的Model Builder建模,以镇江城区为例,采用不同的服务半径阈值,分析了目前镇江城区的餐饮服务业可达性分异情况。研究结果表明：商家服务能力的提升和消费者的生活习惯很大程度影响着餐饮业的可达性指数,Model Builder的流程化建模在一定程度上简化了传统操作流程。     

一种改进的快速浮动车地图匹配方法

浮动车地图匹配算法能够实现浮动车离散点与路段的快速准确匹配,是浮动车路况信息生成技术中的核心环节。本文针对现有方法的不足,实现了建立定位点的有效阈值缓冲区,并依据空间关系检索候选匹配路段,研究实现了一种利用行驶速度、行驶方向、投影距离、行驶距离4个参数进行行车轨迹判别的逻辑匹配算法。试验表明,该方法无需对路网数据进行大量的前期处理工作,简化了候选匹配路段的检索过程,在保证匹配正确率的同时也表现出了更高的效率。     

Experimental studies on performances of flexible floating oil booms in coupled wave-current flow

Floating oil booms are commonly-adopted facility to collect spilled oil on sea surface, or to protect specific areas against oil slick spreading. In this study, 931 runs of laboratory test were carried out under wave-current coupling conditions to investigate hydrodynamic performances of the flexible floating oil boom. The tests first conducted a comparison on motion responses between the flexible floating boom and the rigid one to indicate the necessity of taking the flexibility of boom into consideration. Then a comprehensive analysis was carried out to investigate the effects of the ambient currents, waves and the boom characteristics of material stiffness, diameter of floater, length of skirt, and B/W (Buoyancy/Weight) ratio on the motion responses of the flexible floating booms. Finally, by taking the water blockage effect in front of the boom into consideration in the definition of boom effectiveness, the effective draft and freeboard were compared between the flexible boom and rigid one under fixed current and wave conditions. The effects of currents, waves, skirt lengths and B/W ratios on the effective draft and effective freeboard are assessed.