Towards a seascape typology. I. Zipf versus Pareto laws

Two data analysis methods, referred to as the Zipf and Pareto methods, initially introduced in economics and linguistics two centuries ago and subsequently used in a wide range of fields (word frequency in languages and literature, human demographics, finance, city formation, genomics and physics), are described and proposed here as a potential tool to classify space–time patterns in marine ecology. The aim of this paper is, first, to present the theoretical bases of Zipf and Pareto laws, and to demonstrate that they are strictly equivalent. In that way, we provide a one-to-one correspondence between their characteristic exponents and argue that the choice of technique is a matter of convenience. Second, we argue that the appeal of this technique is that it is assumption-free for the distribution of the data and regularity of sampling interval, as well as being extremely easy to implement. Finally, in order to allow marine ecologists to identify and classify any structure in their data sets, we provide a step by step overview of the characteristic shapes expected for Zipf's law for the cases of randomness, power law behavior, power law behavior contaminated by internal and external noise, and competing power laws illustrated on the basis of typical ecological situations such as mixing processes involving non-interacting and interacting species, phytoplankton growth processes and differential grazing by zooplankton.     

舰船惯导航行数据的重构及混沌特性分析

针对现有舰船航行数据处理研究中,对数据内在属性及不同数据间相关性研究不够深入的问题,应用不同方法对舰船惯导航行数据进行了相空间重构及比较分析。分析结果表明,C-C方法对船舶惯导航行数据的重构效果较好。在此基础上,进行了惯导数据的混沌特性定性分析,并计算了惯导数据的最大Lyapunov指数,对舰船惯导数据进行了混沌动力学特性研究。分析结果证实了舰船航行数据具有较为典型的混沌特性,为进一步研究采用混沌控制等方法对舰船航行中的混沌状态进行控制提供必要的数据基础和比较依据。     

Lagrangian data in a high-resolution numerical simulation of the North Atlantic: I. Comparison with in situ drifter data

A model/data comparison was performed between simulated drifters from a high-resolution numerical simulation of the North Atlantic and a data set from in situ surface drifters. The comparison makes use of pseudo-Eulerian statistics such as mean velocity and eddy kinetic energy, and Lagrangian statistics such as integral time scales. The space and time distribution of the two data sets differ in the sense that the in situ drifters were released inhomogeneously in space and time while the simulated drifters were homogeneously seeded at the same time over a regular 1° grid. Despite this difference, the total data distributions computed over the complete data sets show some similarities that are mostly related to the large-scale pattern of Ekman divergence/convergence.Comparisons of eddy kinetic energy and root mean square velocity indicate that the numerical model underestimates the eddy kinetic energy in the Gulf Stream extension and in the ocean interior. In addition, the model Lagrangian time scales are longer in the interior than the in situ time scales by approximately a factor of 2. It is suggested that this is primarily due to the lack of high-frequency winds in the model forcing, which causes an underestimation of the directly forced eddy variability. Regarding the mean flow, the comparison has been performed both qualitatively and quantitatively using James' statistical test. The results indicate that over most of the domain, the differences between model and in situ estimates are not significant. However, some areas of significant differences exist, close to high-energy regions, notably around the Gulf Stream path, which in the model lies slightly north of the observed path, although its strength and structure are well represented overall. Mean currents close to the buffer zones, primarily the Azores Current, also exhibit significant differences between model results and in situ estimates. Possibilities for model improvement are discussed in terms of forcings, buffer zone implementations, turbulence and mixed layer parameterizations, in light of our model/data comparison.     

高水头省水船闸水工结构及输水系统研究

长江上游地区水头高、流速快、水位变幅大,对通航建筑物提出了较高的要求,采用升船机形式较难解决运量小、高地震烈度对塔柱的横向位移要求等问题;多级船闸形式又面临耗水量巨大、下游引航道流态不佳等问题。省水船闸是解决上述问题的有效结构形式,但在我国的应用经验较为有限。以三峡新通道工程为依托,从省水船闸的工作原理出发,分别对结构选型、省水池布置、结构高程及尺度确定、输水系统的计算流程和参数确定方法等关键问题进行研究,并通过结构核算、输水效率、省水量3个方面说明省水船闸方案的可行性及其相对于梯级船闸的优越性。     

船用柴油发电机组的浮筏隔振及其效果分析

为了减小船用机械振动向船体结构的传递,常采用浮筏隔振系统对船舶设备进行集中隔振。文章对某船用柴油发电机组进行了隔振设计并研究其效果,采用有限元软件MSC Patran建立了隔振系统的动力学模型。首先计算得到了各阶模态,然后分析了隔振系统参数变化对隔振效果的影响,最后研究了不同激励对瞬态动力学特性的影响。计算结果表明,浮筏隔振系统的设计满足隔振要求,隔振性能及抗冲击性能良好。     

舰船辐射噪声的混沌特性检验

为提取舰船目标辐射噪声混沌特征,实现对舰船目标的自动识别,首先需要对舰船辐射噪声的混沌特性进行检验。采用一种改进的Lyapunov指数谱估计方法,计算其最大Lyapunov指数是否大于零,以及所有的Lyapunov指数之和是否小于零来判定噪声时间序列是否具有混沌特性。采用三类舰船目标辐射噪声作仿真计算,仿真结果表明三类舰船辐射噪声都具有一定的混沌特性,该结论为下一步基于混沌预测的目标检测以及提取舰船辐射噪声非线性混沌特征等工作奠定了理论基础。     

船体梁静水载荷效应统计预报

船体梁静水剪力、弯矩等是由装载状态决定的载荷效应。营运船舶装载记录表明，实际装载状态具有不确定性，由此导致载荷效应发生变异，其统计特性可利用回归公式或随机模拟原理进行估算或预报。通过对油船、散货船、滚装船及集装箱船约2000种随机工况所作的统计分析，表明其静水弯矩等随装载偏差的变化近似于正态分布律，并具有比船体中剖面模数或钢材屈服极限更为显著的变异性。在船舶结构可靠性分析或理性设计中，合理估算并预报这种及异性是必要的。     

Production of Acartia omorii (Copepoda: Calanoida) in Ilkwang Bay, southeastern coast of Korea

Production of the marine calanoid copepod Acartia omorii was measured from 2 October 1991 to 8 October 1992 at a station in Ilkwang Bay on the southeastern coast of Korea. A. omorii (nauplii + copepodites + adults) were present in the plankton throughout the year, with seasonal variation in abundance. Biomass of A. omorii was averaged at 0.44 mgC m^− 3, with peaks in February and July, and relatively low biomass in late summer and fall. Egg production rate ranged from 2.4 to 151.9 μgC m^− 3 day^− 1, which was equivalent to 95–6075 eggs m^− 3 day^− 1. Fecundity of an adult female was averaged at 38 eggs female^− 1 day^− 1. Instantaneous growth rates of copepodites were higher than those of nauplii stages. Annual production of A. omorii ranged from 33.5 mgC m^− 3 year^− 1 to 221 mgC m^− 2 year^− 1, showing a seasonal variation of daily production rate with peaks in February and July. The daily production rate of A. omorii was significantly correlated with chlorophyll a concentration. These results suggest that standing stocks and/or productivity of phytoplankton are the major influencing factors, rather than water temperature for the seasonal variation of production of A. omorii in Ilkwang Bay.     

FPSO外输系统维修策略研究

浮式生产储油轮(FPSO)是当今海洋石油天然气开发的主要设备之一。针对外输系统作为FPSO重要的一个子系统,但其传统维修策略过于依赖经验的缺陷,从可靠度角度出发,通过对失效模式和失效概率的分析从而确定较为合理的检修周期和大修周期。采取失效模式和效果分析（FMEA）方法确定主要失效模式及其关系,再利用动态故障树分析（DFTA）方法获得最小割集及相应故障时间,最后通过成组维修理论从全局最优化,经济性角度确定大修周期约为3.23年。经过与工程实际数据的对比,验证了该方法的可行性和适用性。     

Chlorophyll estimation in the Southeastern Mediterranean using CZCS images: adaptation of an algorithm and its validation

Region-specific algorithm to derive chlorophyll concentration from Coastal Zone Color Scanner (CZCS) images was adopted following field measurements in the Southeastern Mediterranean Sea, in June 1992. Reflectance in the range 400 to 700 nm, chlorophyll concentration and seston dry weight were measured simultaneously at 21 stations. The optical model used based on algorithm for Case I waters, using shipboard simulation of CZCS channels for adaptation of parameters. The resulting model was validated with an independent data sets from series of cruises in the Southeastern Mediterranean (1981–1984). Concurrent CZCS images were used for retrieval of the radiance ratio Channel 1/Channel 3, for each station. The resulting ratios were then used to calculate chlorophyll concentrations. A comparison between those calculated concentrations and the actual chlorophyll measurements showed that an estimation error of chlorophyll as low as 0.013 mg m⁻³ was achieved.     

港口吞吐量增长率对吞吐量预测的影响与实证分析

目前对港口吞吐量的预测方法例如时间序列法、因果关系分析法、概率预测技术等都是基于已有吞吐量数据进行预测,对吞吐量的增长率规律考虑较少,因此往往难以估计误差上下限。文章通过增长率的发展规律对港口吞吐量预测进行估计,并针对鹿特丹港进行实证比较。     

Error quantification of a high resolution coupled hydrodynamic-ecosystem coastal-ocean model: Part3, validation with Continuous Plankton Recorder data

Data collected during the Continuous Plankton Recorder (CPR) survey has been used to validate a three-dimensional hydrodynamic ecosystem model simulation of the North-west European Shelf for the years 1988–89. The CPR time series is unique to the North Atlantic region as a validation tool. Data were extracted from the model to correspond with those collected by the CPR survey, and both the model and survey plankton data were standardised to allow the comparison of model biomass with survey counts. Simple linear regression and absolute error maps provide a qualitative evaluation of spatio-temporal model performance of simulated diatoms, flagellates, total phytoplankton and omnivorous mesozooplankton. Comparisons of z-scores indicate that the model reproduces the main pelagic seasonal features, and there is good correlation between magnitudes of these features with respect to standard deviations from a long-term mean. The model is replicating up to 62% of the mesozooplankton seasonality across the domain, with variable results for the phytoplankton. There are, however, differences in the timing of patterns in plankton seasonality. The validation exercise has highlighted that the spring diatom bloom in the model is too early, suggesting the need to reparameterise the response of phytoplankton to changing light levels in the model. Errors in the north and west of the domain imply that model turbulence and vertical density structure need to be improved to more accurately capture plankton dynamics.     

海港工程活动式防浪结构有限元分析

针对一种新型海港活动式防浪结构,基于有限元法建立4种分析模型进行模拟计算。对比分析可知,利用接触面上节点自由度耦合方式创建的有限元模型更适用。运用上述有限元模型,分别对活动式防浪结构的应力、位移和螺栓内力进行求解,以及分析钢材厚度变化对组合结构力学性能的影响。结果表明:钢构件下端拉、压应力较大,需重点加强;板厚越小,组合结构的应力和变形越敏感。结合防浪结构的安全性和经济性,提出设计和优化要点,为工程应用提供参考。     

天津港二突堤转角区域码头结构与土体三维有限元分析

近年码头调查发现,天津港多个突堤转角区域的码头结构变形和横向错位情况十分严重,这与以前发现和认识的规律有所不同。文中从这些问题入手,以天津港二突堤为对象,系统地研究了该突堤转角区域码头结构和岸坡相互作用机理和变形特点,并指出突堤转角区域的码头结构受力比较复杂,其变形具有空间变化特点,传统的二维分析和设计方法是不够全面的。     

基于近似约简的基因选择方法

为了对癌症等疾病分型、诊断及进行病理学研究,利用基因微阵列数据识别疾病相关基因.考虑到了基因微阵列数据是典型的矛盾决策系统,在证明矛盾系统在近似分布集上是协调的这一事实的基础上提出了一套近似分布约简理论,讨论了不同近似分布集上约简之间的关系,提出了基于近似约简的基因选择方法.使用两组真实的基因表达数据对所提出的方法进行了验证.实验结果表明,该方法能在保持分类能力的情况下降低特征基因集的相关性,从而显著地减少特征基因的数量.     

基于PCA与属性权重模糊聚类的入侵检测方法

针对入侵检测数据集中存在大量冗余信息及传统聚类算法的效果不佳,提出了结合主成分分析与属性权重模糊聚类算法的入侵检测方法。该方法分为特征提取和模糊聚类两阶段,使用主成分分析进行特征提取、消除冗余属性;将经主成分分析后得到新成分的贡献率作为聚类算法中属性的权重值,实现了基于属性权重的模糊聚类。在KDD-CUP99数据集中的实验结果表明,该方法能有效地降低检测训练时间和提高检测正确率。     

Probabilistic time series prediction of ship structural response using Volterra series

This study targets to develop a computational procedure to predict the structural response of a ship voyaging through irregular seaways taking into account the relevant uncertainties from probability perspective. To achieve the goal, ship structural response under random wave excitation was assumed to be linear one and represented by linear Volterra series, which is expanded by linear combination of Laguerre polynomials. Then the unknown Laguerre coefficients were treated as random variables, the probability of which was sought by solving Bayesian linear regression model using prepared data sets. For the validation of the proposed methodology, a single DOF linear oscillator model with artificial damping uncertainties was introduced and time series of the system response was predicted probabilistically. For more practical and realistic application, 400,000 DWT VLOC model ship experimental data was analyzed and vertical bending moment time series were probabilistically predicted using the proposed method. On top of probabilistic time series prediction of model ship, the fatigue damage was also estimated based on the stochastic time series obtained using predicted probabilistic time series data.     

直线感应电机屏蔽层的涡流场和开孔分析

从直线电机屏蔽层出发,研究屏蔽层涡流场的分布、不同频率对屏蔽层涡流损耗的变化情况以及屏蔽层开孔是否带来涡流集中,并将矢量电位法计算和有限元分析结果与试验数据进行对比,验证分析的正确性。     

Strain prediction for critical positions of FPSO under different loading of stored oil using GAIFOA-BP neural network

FPSO (floating, production, storage and offloading) units are widely used in the offshore oil and gas industry. Generally, FPSOs have excellent oil storage capacity owing to their huge oil cargo holds. The volume and distribution of stored oil in the cargo holds influence the strain level of hull girder, especially at critical positions of FPSO. However, strain prediction using structural analysis tools is computationally expensive and time consuming. In this study, a prediction tool based on back-propagation (BP) neural network called GAIFOA-BP is proposed to predict the strain values of concerned positions of an FPSO model under different oil storage conditions. The GAIFOA-BP combines BP model and GAIFOA which is a combination of genetic algorithm (GA) and an improved fruit fly optimization algorithm (IFOA). Results from three benchmark tests show that the GAIFOA-BP model has a remarkable performance. Subsequently, a total of 81 sets of training data and 25 sets of testing data are obtained from experiment using fiber Bragg grating (FBG) sensors installed on the surface of an FPSO model. The numerical results show that the GAIFOA-BP is capable of predicting the strain values with higher accuracy as compared with other BP models. Finally, the reserved GAIFOA-BP model is utilized to predict the strain values under the inputs of a 10-day time series of volume and distribution of stored oil. The predicted strain results are further used to calculate the fatigue consumption of measurement points.     

开敞水域中斜跨航槽水流的流速计算

通过理论分析,运用试验数据,对开敞水域航槽中心垂线平均流速变化规律进行探讨,同时给出了航槽中心垂线平均流速的计算公式。在表达式中,边坡采用了比以往幂函数更为合理的指数函数形式。最后,用水槽试验数据对所得公式进行必要的验证,计算值与实际值吻合较好。