一种水池中组合活动堰的潮位潮流模拟系统

水工模型实验中,潮流模拟系统往往控制复杂,且调试困难。本文给出一种用单板机控制步进电机驱动高低组合活动堰板造潮的水动力控制系统,经实验验证,本系统控制简单,调试方便,造价低廉。     

Seawater Corrosion Fatigue of Welded Joints Under Random Variable Amplitude Loading

- Offshore platforms are always subjected to wave action which is random variable amplitude cyclic loading. In order to simulate the stressing condition at the 'hot spot' of the tubular joints and the marine environment, random variable amplitude fatigue tests have been carried out on welded plate joints in sea water. The tests have been conducted under the conditions of loading frequency of 0.2 Hz, stress ratio of -1, seawater temperature of about 20℃ and cathodic protection with the potential about -850 mV, SCE. The test results have been compared with the seawater corrosion fatigue life under constant amplitude loading. Miner's linear cumulative damage summation rule has been used to predict the corrosion fatigue life under variable amplitude loading. The predicted life is in good agreement with the test data.     

Buckling of circular, annular plates of continuously variable thickness used as internal bulkheads in submersibles

This paper deals with the determination of the critical load in the buckling of isotropic, circular annular thin plates whose thickness varies slightly according to an exponential law.The outer edge of the plate is elastically restrained against rotation while the inner boundary is free. Classical small-deflection theory is used. An hidrostatic pressure acting in the middle plane is considered.The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. It is shοwnι that the results are in good agreement from an engineering viewpoint, with those available in the literature.     

Mats of Beggiatoa bacteria reveal that organic pollution from lumber mills inhibits growth of Zostera marina

The objectives of this study were to determine the distribution and abundance of Zostera marina (eelgrass) in relation to the distribution of the mat forming bacteria Beggiatoa spp., and the levels of sulfide and organic material (wood waste) in the sediment. Underwater videography and intertidal surveys were used to map the distribution and abundance of Z. marina beds and Beggiatoa in the nearshore area of Commencement Bay, WA (USA), a location that has a long history of sawmill activity. Zostera marina occurred from the intertidal to ?6 m mean lower low water (MLLW) on sandy substrates in areas with low levels of sulfide (<50 μm ) and organic material (<5 % total volatile solids). Areas with high sulfide levels (>200 μm ) occurred where there were significant amounts of organic material in the sediments, which was found to be wood waste that had been discarded from sawmills. Zostera marina was absent from the intertidal and occurred at lower densities in areas with high sulfide levels. In contrast, mats of Beggiatoa were only found in areas where the sulfide levels were >1000 μm and there were significant deposits of wood. Thus, the negative correlation between the distribution and abundance of Z. marina and Beggiatoa suggests that the presence of Beggiatoa mats could be used as a biological indicator of inhibiting levels of hydrogen sulfide in the marine environment.     

自适应遗传算法解决集装箱装载问题的方法探讨

集装箱装箱问题是1个有很强应用背景的组合优化问题，约束条件多，求解极为困难。本文探讨了自适应遗传算法在复杂集装箱装载问题中的应用，算法中采用跨世纪精英选择策略保持了群体的多样性，并给出了有效的解码算法。实例仿真结果显示出很好的效果，同等条件下求解结果比使用启发式算法高出近10个百分点，表明该算法是行之有效的。     

Experimental Study on Rectangular Floating Breakwaters

This paper proposes ten types of improved floating breakwaters for experiment with regular waves, based on the experience in the development and manufacture of existing floating breakwaters both at home and abroad, and on the results of experimental studies on the hydraulic characteristics of several types of floating breakwaters. The wave heights before and behind the breakwaters are measured, the movements of floating breakwaters are observed and the chain forces of the floating breakwaters are measured. The paper studies and compares the hydraulic characteristics of the improved rectangular floating breakwaters of which the internal and external structures and their installation methods are changed. Finally the optimal type of structure is selected through experiments.     

波浪作用下软基上沉入式大直径圆筒结构的变位计算模型

文章通过所建立的软粘土地基土体的循环累积变位分析模型，对大直径圆筒原型结构在波浪引起的水平向循环荷载作用下的基础稳定性进行研究，计算分析了简体随循环次数的变位状况和临界稳定状态时简体所受到的土压力分布以及临界稳定状态的判别参数c值。     

Finite Element Analysis of soft Foundation Strengthening by Vacuum Loading from Lower Position

Strengthening soft foundation by vacuum loading from lower position is a new method of ac-celerating the consolidation of dredger fill.This paper presents the mechanism of soft foundation strength-ening by vacuum loading from lower position and evaluates the effectiveness of this method under variousboundary conditions by means of finite element method(FEM)on the basis of Biot's consolidationtheory.     

淹没状态下半圆型防波堤的水力特性研究

以淹没状态下的半圆型防波堤为研究对象,采用不规则波断面模型试验,结合典型实例分析了堤体波压分布的特点,指出波浪经过堤顶破碎与否直接影响到堤体所受波力的大小,并建议了开孔办法和波力计算方法.