自升式平台桩靴结构优化设计

结合有限单元法和尺寸优化理论,对某自升式海洋平台的桩靴结构进行了设计与优化。根据桩靴设计要求确定各部件尺寸和相应材料参数,以此建立桩靴的有限元模型。针对CCS对桩靴提出的工况依次进行分析计算,获得各工况下应力与位移的分布特征和土壤作用力在结构中的传递路径。然后进行板厚尺寸的优化。计算结果表明,桩靴在偏心工况且偏心角度为60°时应力达到最大,且土壤流失可能性最高;尺寸优化后,桩靴的质量明显减少,应力分布更加均匀,材料利用率得到有效提高。     

Managing Shoreline Change Under Increasing Sea-Level Rise in Ghana

Relative sea-level rise will affect vulnerable coastal communities globally. Quantifying this effect on the coastal environment and infrastructure provides critical information that enables coastal managers to develop sustainable mitigation and adaptation measures. Modeling applications have enabled the past, present, and future trends in shoreline morphology to be investigated in detail. Predictive numerical models depend largely on the reliability of the input data. This article reports on using the Soft Cliff and Platform Erosion (SCAPE) numerical model to simulate future shoreline evolution trend in the central Accra coast in Ghana. The model input parameters include historic shoreline recession rates, wave data, tidal data, bathymetry, beach volume, beach topography, historic relative sea-level rise rates, and the shoreline orientation. The data fed the SCAPE numerical model which simulated the emergence of soft rock shore profiles over timescale of decades to centuries, to project future positions of the central Accra shoreline for the next 100 years under different scenarios of climate change. Simulated future shoreline positions overlaid on a 2005 orthophoto map of Accra enabled vulnerable areas and infrastructure at risk to be identified. It emerged that a highly populated community in central Accra will be inundated by 2065, while the Rivera beach resort will be eroded from 2035. A natural fish landing site in Osu (suburb in Accra) will be lost from 2045. The study has demonstrated that considerable ecological, economic, social, and national losses should be expected within the next century. Shoreline change management options should be explored to help mitigate the expected impact of the sea-level rise.     

Northern Abalone: Using an Invertebrate to Focus Marine Conservation Ideas and Values

Marine invertebrate species have usually been overlooked in favor of high-profile vertebrate species for facilitating dialogue towards area conservation. The northern abalone (Haliotis kamtschatkana) is proposed as a focal ("flagship") species whose protection and recovery could concentrate public concern for abalone and its associated kelp forest ecosystems in Haida Gwaii (Queen Charlotte Islands), British Columbia. I explain how issues of culture, commerce, and conservation unite to create a strong role for northern abalone in preparations for creating a large marine conservation area within Haida Gwaii. Culture is relevant, as local indigenous people (the Haida) are currently denied access to constitutionally established subsistence fishing rights for northern abalone. Commerce is involved as ongoing kelp forest-associated fisheries co-occur with northern abalone. Finally, this is a challenging precedent in Canadian marine conservation, as restoring two "listed" species- at risk (northern abalone and their predator, the sea otter (Enhydra lutris)) is potentially mutually exclusive. As part of the forthcoming public consultations towards establishing a marine conservation area, the opportunity provided by northern abalone to focus ideas and values should be seized.     

Some economic aspects of conflicts over land use in the coastal zone

Abstract

Recent land use legislation pays particular attention to the coastal zone where age‐old conflicts have recently accelerated. Flexibility is required in policy because visible conflicts are tied into complex physical and social systems which may require changing patterns of land use over time. Public policy is altering property rights and a thorough understanding of the economic and social roles played by those rights is required. Economic models can be used to understand some major changes such as types of alteration of the environment, but may be ignored or misused unless a better understanding of coastal decision processes is developed.     

高性能清水混凝土耐腐蚀性能及水化微观试验研究

高性能清水混凝土通过使用一些掺合料和外加剂来增强其抗物理侵蚀和耐化学腐蚀性能。通过分析高性能混凝土抗渗透、抗污染、抗干湿交替破坏、耐碳化、耐风化及耐氯离子和硫酸盐侵蚀性能,评价了高性能混凝土的优势,然后采用微观SEM试验对掺合料与外加剂对水化性能的影响进行试验分析。结果表明：将粉煤灰或者矿渣粉取代水泥可以提高水化程度,增大C—S—H凝胶含量,起到微孔隙填充和＂微纤维配筋＂效果,从而增大了混凝土的密实度和强度性能。     

合义渠西支渠中桥桩柱结合处混凝土破损病害成因及处理方法

高速公路跨河桥梁由于长期受到河水的冲刷而出现桩、柱混凝土破损现象。鉴于此,就这一病害的成因以及维修方法进行详细的介绍,以期为同类桥梁的病害治理提供参考与借鉴。     

淮河出海航道滩头整治工程平面方案分析

航道整治需抓住工程实施的有利时机,在通航条件还未恶化前提前预防。以淮河出海航道(红山头—京杭运河段)大淤滩整治工程为例,利用平面二维水流数学模型对滩头不同侵蚀方案产生效果进行计算,分析若不对滩头进行守护将可能导致的后果,说明滩头守护的必要性,并结合河床演变分析提出滩头整治工程平面布置方案。     

一种实用的配电网潮流算法

目前matlab潮流计算程序多是基于输电网开发,而对配电网中潮流计算程序较少开发。配电网由于其特有的辐射性、R／X较大、节点较多的特性,导致用于输电网的潮流计算方法由于收敛性问题并不适用于配电网系统中。针对辐射性配电网的特点,开发了用于配电网潮流计算的matlab程序,该程序采用新的支路选择方法,无需对网络进行复杂的编号,并通过算例验证了程序的正确性。     

重交通下路基材料抗冲刷性能的研究

针对水泥粉煤灰稳定碎石、石灰粉煤灰稳定碎石、石灰粉煤灰砂砾不同配比的抗冲刷性能进行对比试验,根据试验结果．提出南方地区重交通条件下路基材料的最佳配比,可为设计适应路基高强度、低开裂、抗冲刷性能好的路基基层提供参考。     

基于滑膜控制的半挂汽车自动倒车路径跟踪

文章针对半挂汽车倒车时的跟踪控制问题进行了研究,建立了该系统在卡迪尔坐标系下的车辆非线性运动模型.为了简化求解过程,通过准确线性变换方法对建立的系统进行了线性化,设计了滑膜变结构控制器,基于Ackermann公式进行极点配置选取控制参数,最后对直线倒车路线的跟踪控制进行了仿真分析.仿真结构表明:设计的反馈控制器能改善半...