大叶藻的生态学特征及其与环境的关系

大叶藻是近海生态系统中重要的初级生产者。本文从5个方面论述了大叶藻的生态学特征及其与环境的关系:1)大叶藻对海洋沉水生活的适应;2)大叶藻在资源分配上的繁殖策略;3)大叶藻的营养盐代谢;4)大叶藻对近海生态的贡献;5)大叶藻衰退的原因。     

Fatigue Properties of Plain Concrete Under Triaxial Compressive Cyclic Loading

Experiments were made on plain concrete subjected to triaxial static loading and constant-amphtude compressive fatigue loading with a constant lateral pressure in two directions. The initial confining pressure was O, O. lfc, O. 25fc and O. 4fc, respectively, for the static test, and O. lfc and O. 25fc for the fatigue test. Based on the triaxial compressive constitutive behavior of concrete, the inflexion of confining pressure evolution was chosen to be the fatigue damage criterion during the test. The rule of evolution of longitudinal maximum and minimum strains, longitudinal cyclic modulus and damage were recorded and analyzed. According to the Fardis-Chen criterion model and the concept of equivalent fatigue life and equivalent stress level, a unified S-N curve for multi-axial compressive fatigue loading was proposed. Thus, the fatigue strength factors for different fatigue loading cases can be obtained. The present investigation provides information for the fatigue design of concrete structures.     

Life Cycle,Growth and Secondary Production in a Brackish-Water Population of the Polychaete Notomastus latericeus (Capitellidae) in the Mediterranean Sea

Abstract. Three years of observations on a population of Notomastus latericeus Sars from Acquatina lagoon (Lecce, Italy) are reported. The population dynamics, life cycle, and reproduction were investigated in order to explain periodic density variations of this species. Some physical parameters of the water column were measured and sediment analyses were performed to characterize the environment. Secondary production was also estimated as part of a functional study of the benthic system in the Acquatina lagoon. The species is opportunistic; its density is apparently correlated to variation in salinity, but its presence in the lagoon is dependent on recruitment success and competition with other polychaete species.     

基于人工神经网络的混凝土疲劳寿命估算

把决定混凝土疲劳寿命的应力水平，应力比，加载频率和描述随机性的破坏概率作为神经网络的输入，以疲劳寿命作为网络的输出，用网络结构描述它们之间的非线性关系，利用实验数据样本完成了网络的训练，并对模拟样本进行了估算，实例计算了结果表明，利用已有疲劳试验数据训练好的人工神经网络进行混凝土疲劳寿命估算，可部分代替冗长，昂贵的疲劳实验。     

Fluctuations and Variations in Coastal Marine Environments

Abstract. The manifold aspects of variability of coastal marine ecosystems are reviewed, with special reference to the response of species and communities. Fluctuations are defined as recurrent modifications in community structure, for instance due to seasonality, whereas variations are defined as changes permanently leading from a given community to a different one. Both patterns are described and linked to the interaction between life history traits and environmental factors. Resting stages are proposed to play a still underestimated role in the dynamics of coastal communities, especially for plankton. Rare species are considered as an essential constant of communities, being the source of potential variation and alternance in the contribution to the standing biomass.     

Research on Fatigue invalidation of A Submarine Pipeline Span Subjected to Waves and Currents

1 .IntroductionRecently, more and more importance is attached to the development of offshore oil and gas alloverthe world and many submarine pipelines have been laid.Submarine pipelines are the lifeline ofthe transportation of offshore oil and gas .Submar…