主动式声纳列阵拖曳系统姿态数值计算

主动式声纳列阵拖曳系统是用于探测潜艇的新型声纳系统，为了准确探测潜艇的位置，必须首先预报声纳列阵的瓷态，本文通过对其三维力学模型的分析，得到该系统的运动微分方程，其中缆索的力学方程是基于Ablow和Milinazzo的模型，而对于拖体则运用六自由度空间运动方程模拟，结合边界条件，用有限差分法求解，通过对拖船的不同运动状态如匀速，变速和回转的计算，证明本文的方法对于预报声纳列阵的姿态是有效的。     

6000m深海拖曳系统动力响应计算

本文数值计算了６０００ｍ深海单拖体和双拖体拖曳系统的动态响应，特别是研究了拖船的垂荡运动对拖体定高性的影响。对于双拖体系统，本文对第二拖体在水中的重量、联接两拖体的缆索长度及其在水中重量等因素对第二拖体定高性的影响进行了详细的计算、分析。计算表明，采用双拖体系统可大大提高系统的定高性。     

海洋测量水下拖曳设备的位置计算方法研究

针对海洋测量水下拖曳设备位置确定问题,综合考虑拖缆受力、海流影响以及水下拖体的运动性质,建立了水下拖曳设备的位置计算模型,并仿真计算分析了测量船在不同航行状态下拖曳设备位置确定的规律,探讨了不同海流效应对拖曳设备位置确定的影响。仿真计算结果表明,在海洋动态环境作用下,拖缆各方向的偏移明显呈曲线形状,非简单几何运算所确定。测船各方向的运动均可对水下拖体的位置在相应方向产生一定影响,而水下拖体位置的变化量小于测船拖点位置的变化量。海流对水下拖曳设备定位可造成数米的偏差,需进行相应改正。建议可考虑采取船载式ADCP实时测流辅助水下拖曳设备定位的工作模式。     

水下拖曳升沉补偿系统水动力数学模型研究

建立变缆长的水下拖曳升沉补偿系统水动力学偏微分方程组和边界条件.拖缆动力学模型基于Ablow and Schechter模型,拖体采用水下运载体六自由度方程模拟,运用有限差分法离散偏微分方程组和牛顿迭代法计算变缆长情况下拖体深度与拖缆各点张力的动态取值.数值计算结果表明采用收放拖缆的升沉补偿方法能够有效削弱母船升沉运动对拖体深度和拖缆张力的影响.     

带翼声纳拖体的稳定性问题及三点拖曳方式

本文对带翼拖体的稳定性通过理论分析,得到在拖速改变时仍能保持正浮稳定拖曳的条件。在船模试验池中对六种水翼模型分别同一个拖体模型拼装的组合体进行了各种拖曳试验。试验证实,作者有关带翼拖体正浮稳定拖曳条件的理论分析是正确的。试验还表明,利用三点拖曳笼头与纵倾角传感器能迅速自如地找正各种带翼拖体的正浮稳定拖曳点位置,从而在技术上解决了带翼拖体的稳定性问题。     

海上拖缆地震勘探前导缆动态响应预报与分析

拖缆地震采集作业时前导缆的最大悬垂深度及所受拉力对作业安全有重要影响,需对其进行分析计算和预报。本文首先对多缆拖曳系统各缆索和拖体的连接关系和受力进行了理论分析,随后采用OrcaFlex软件对12缆拖曳系统中涉及的船舶、前导缆、扩展器、主辅拖带绳和缆间扩展绳等多个构件进行建模,计算得到了船-多缆-多体的拖曳系统耦合动态响应结果,对比不同航速下前导缆的最大悬垂深度及拉力极值,分析航速对两指标的影响。最后,模拟在前导缆上加设浮鱼后的响应结果,并与海上实测结果进行对比,验证了数值模拟方法的可靠性,为实际作业中前导缆的响应预报和布缆设计提供参考依据。     

海洋磁力仪拖体入水深度试验与分析

拖体入水深度是水下拖曳作业的主要参数,其取决于拖体自身重量、拖缆长度和船速。通过G882TVG海洋磁力仪阵列的拖曳试验,分析了船速、配重、拖缆长度的相互关系,导出拖体入水深度计算模型,对类似设备的拖曳参数确定具有借鉴意义。     

振荡剪切流作用下钢悬链线立管非线性动力分析

钢悬链线立管(SCR)的非线性动力响应会在复杂的海洋环境下发生改变。以钢悬链线立管为研究对象,采用细长柔性杆理论,考虑波浪与振荡剪切流联合作用,建立钢悬链线立管运动方程并进行有限元离散,在时域中求解,编写相应计算程序,通过算例研究钢悬链线立管在波浪与振荡剪切流联合作用下的动力响应变化规律。将振荡剪切流与一般剪切流进行对比,得到突发海况下振荡剪切流对钢悬链线立管动力响应的影响规律,为复杂海洋环境下的工程设计提供依据。     

拖曳线列阵阵形与姿态数值计算

本文提出的计算程序ＣＡＢＬＥ能预报拖缆系统中拖曳线列阵的三维运动,同时可计算各时刻缆索及列阵上相应的应力。系统的运动方程与Ａｂｌｏｗ［１］提出的相似,采用有限差分法计算求解。程序能够计算不同航速定常直航状态下列阵的阵形与姿态,可解决不定常运动（例如回转运动）、考虑流速以及船舶有升沉等多种运动状况的阵形预测。所得结果与其它计算及试验所提出的结果显示出良好的一致性。程序所花计算时间少,计算可靠。程序可运用于实际操作中。     

拖曳系统计算中拖缆与拖体的耦合计算

针对带有水下设备舱的拖曳系统,提出了一种有效的算法,来获得拖曳系统的运行状态。将拖曳系统分成拖缆和水下拖体两个部分,分别建立运动数学模型。拖缆部分的模型以Ablow和Schechter的运动数学模型为基础;拖体部分的模型采用类似潜器的水下六自由度运动方程。将这两部分方程联立,统一求解,解决两个模型之间的耦合问题。经过数值仿真的检验证明算法具有可行性。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Evaluation of the Risk of Marine Slope Instability: A Pseudo-3D Approach for Application to Large Areas

This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.