作用于平台桩腿的海冰屈曲破坏冰压力随机过程模型及其参数确定

冰对结构的作用过程是典型的随机过程。本文在冰压力过程为平稳过程的假设下，从渤海海冰对平台桩腿作用的大量实测冰压力数据中，选取了２１条冰屈曲破坏时的冰压力时程曲线，对它们进行谱分析后，得到了单点冰屈曲破坏的压力随机过程的谱密度，并确定了谱参数及其跟环境要素的关系，依据文献［１］中冰压力沿圆柱面的空间分布，建立了绕桩腿的冰压力随机场模型，并得到了作用于桩腿的总冰力随机过程及其谱密度。本文的研究成果为平台结构冰激随机振动和疲劳累积损伤分析提供了荷载基础     

黄海表面水温场的准周期变化分析

本文用能谱方法分析了黄海的海表面水温(SST)场的准周期变化。由分析结果清楚地看出,SST具有高频准周期变化:黄海北部以2.6—3.2,1.4—1.7,3.6—3.8和6.7个月的准周期为主;3.3—3.6,5,1.3—2.3及6.7个月在黄海南部占优势。同时,两个海域都有6.7和3.3年的明显的准周期变化。     

Dynamic Analysis of a Single-Column Platform (II)

This paper describes the study of a single-column structure used as well-head platform. In order to check the reliability of computation theory and programme, model tests have been carried out. The paper introduces the conclusion of tests and the dynamic properties of single-column platform are obtained.     

Numerical Simulation of Multi-Directional Random Seas

Multi-directional irregular waves are simulated on the basis of the given directional spectrum using a double summation model, a single direction per frequency model and a single summation model. Their results are compared. It is shown that the single direction per frequency model proposed in this paper can generate a realistic wave field. The effects of the model parameters on the simulated results are also studied in this paper and corresponding suggestions are given.     

基于矢量信号处理的水声定位系统

将传统的水声定位系统与矢量水听器相结合，设计了一种全新的轻便型长基线被动水声定位系统。介绍了系统的组成和工作原理，并结合近年来出现的矢量信号处理技术，设计了新的实时信号处理软件。经湖试和海试，系统的可行性得到了初步的验证。     

引入差比关系法分析西北太平洋TOPEX/POSEIDON卫星高度计测高数据

TOPEX/POSEIDON(T/P)卫星高度计数据信息中存在周期成分混淆问题.对其中的一类混淆引入差比关系方法对混淆的分潮进行分离.卫星轨道交叉点资料包括升轨和降轨资料,资料量比沿轨点资料多1倍,经分析发现:在已有为期6a多的观测资料时间序列中,在沿轨处混淆的分潮如K₁和SSA在交叉点处不再混淆,可以直接分离.因此首先对交叉点资料进行调和分析.然后由交叉点的分析结果得到分潮间的差比关系,处理到相近的沿轨点处,从而得到沿轨点的调和常数.用引入差比关系方法,对西北太平洋海区6a多的T/P卫星高度计资料进行了潮汐分析,并与沿岸及岛屿验潮站资料进行了比较,所得结果较满意.     

Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment

Carbon and nitrogen stable isotope ratios (¹³C and ¹⁵N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The ¹³C and ¹⁵N of surface sediments in the estuary of the Yodo River were less than –23 and 5 respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving ¹³C of about –20 and ¹⁵N about 6). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.     

Assessment of spatial variation in carbon utilization by benthic and pelagic invertebrates in a temperate South African estuary using stable isotope signatures

Stable isotope analyses (δ¹³C and δ¹⁵N) were used to evaluate the spatial variations in carbon flow from primary producers to consumers at two sites in the temperate and permanently open Kariega Estuary on the southeastern coast of South Africa during October 2005 and February 2006. One site was located opposite a salt marsh while the second was upstream of the marsh. Except for significantly enriched δ¹³C values of Zostera capensis and surface sediments near the salt marsh, the δ¹³C and δ¹⁵N signatures of the producers were similar between sites. The invertebrates were clustered into groups roughly corresponding to the predominant feeding modes. The suspension feeders showed δ¹³C values closest to the seston, whereas the deposit feeders, detritivores and scavengers/predators had more enriched δ¹³C values reflecting primary carbon sources that were likely a combination of seston, Spartina maritima and Z. capensis at the upstream site, with an increased influence of benthic algae and Z. capensis at the salt marsh site. The δ¹⁵N signatures of the consumers showed a stepwise continuum rather than distinct levels of fractionation, indicating highly complex trophic linkages and significant dietary overlap among the species. Consumers exhibited significantly enriched δ¹³C values at the salt marsh site, an effect that was attributed to enriched Z. capensis detritus in this region in addition to increased phytoplankton biomass in their diets compared with invertebrates living upstream. The data reinforce the concept that between-site variations in the stable isotope ratios of consumers can result not only from dietary shifts, but also from alterations in the isotope ratios of primary producers.     

Estimation of Uplift Capacity of Rapidly Loaded Plate Anchors in Soft Clay

Plate anchors are extensively used in civil engineering constructions as they provide an economical alternative to gravity and other embedded anchors. The rate of loading is one of the important factors that affects the magnitude of soil resistance as well as soil suction force. This article outlines the effect of pullout rate on uplift behavior of plate anchors (70 mm diameter) buried in soft saturated clay by varying the pullout rate from 1.4 mm/min to 21.0 mm/min. The variation of breakout force and suction force with embedment depth and rate of pull are presented. A correlation between the rate of increase of undrained strength of clay and anchor capacity with rate of strain has been established. Finally an empirical equation has been proposed that includes the rate of pull in the estimation of breakout capacity of anchors.     

Stress Sharing Behavior and Its Mechanism during Consolidation Process in Composite Ground Improved by Sand Compaction Piles with Low Replacement Area Ratio

In order to accurately design a sand compaction pile (SCP) with low replacement area ratio, it is important to understand the mechanical interaction between the sand pile and clay ground and its mechanism during consolidation process in composite ground. In this article, therefore, a series of numerical analyses on composite ground improved by SCP with low replacement area ratio were carried out. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, were confirmed by comparing the results obtained from a series of laboratory model tests with the composite ground improved by SCP. Through the results of the numerical analyses, mechanical behavior of the sand pile and clay in composite ground during consolidation is elucidated, together with a stress sharing mechanism between sand pile and clay.