Underwater video reveals decreased activity of rocky intertidal snails during high tides and cooler days          下载免费PDF全文

Austin W. Taylor  Steven G. Morgan  Sarah A. Gravem 《Marine Ecology》2017,38(2)

Nearly all of our understanding of rocky inter‐tidal ecology comes from studies conducted at low tide. To study inter‐tidal organisms at high tide, we anchored waterproof digital GoPro^® video cameras in wave‐exposed tidepools and recorded the daytime movements of the black turban snail, Tegula funebralis, over the tidal cycle between May and August 2012 near Bodega Bay, California. Overall, snails moved more quickly and presumably foraged more during low tides and on days with warmer air and perhaps water temperatures. This is similar to other ectotherms that exhibit increased metabolic rates, movement and foraging in warmer conditions. Snails also moved less during flood and high tides, may have moved downward in tidepools at flood tides, and showed evidence of reduced activity on days with larger waves. This inactivity and refuge seeking may have been a strategy to avoid dislodgment by waves. Analysis of snail trajectories showed foraging bouts indicated by alternating zig‐zagging and straight movement. There was no effect of temperature, wave height, or tidal phase on distribution of snail turning angles, suggesting that they may have foraged consistently but moved faster during warm conditions and low tides, thereby grazing a larger area. This is one of few direct recordings of inter‐tidal organisms on wave‐exposed rocky shores during high tide. The methods used here are easily transferable to other studies, which are needed to increase our understanding of behaviors that structure rocky shore communities during high tide.  相似文献   

Parametric Geometric Model and Hydrodynamic Shape Optimization of A Flying-Wing Structure Underwater Glider     

WANG Zhen-yu  YU Jian-cheng  ZHANG Ai-qun  WANG Ya-xing  ZHAO Wen-tao 《海洋工程》2017,(6):709-715

Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider''s flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment (DOE) theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization (PSO) algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.  相似文献   

Hydrodynamic Modeling with Grey-Box Method of A Foil-Like Underwater Vehicle   总被引：1，自引：0，他引：1  

LIU Xin-yu  LI Yi-ping  WANG Ya-xing  FENG Xi-sheng 《海洋工程》2017,(6):773-780

In this study, a dynamic modeling method for foil-like underwater vehicles is introduced and experimentally verified in different sea tests of the Hadal ARV. The dumping force of a foil-like underwater vehicle is sensitive to swing motion. Some foil-like underwater vehicles swing periodically when performing a free-fall dive task in experiments. Models using conventional modeling methods yield solutions with asymptotic stability, which cannot simulate the self-sustained swing motion. By improving the ridge regression optimization algorithm, a grey-box modeling method based on 378 viscous drag coefficients using the Taylor series expansion is proposed in this study. The method is optimized for over-fitting and convergence problems caused by large parameter matrices. Instead of the PMM test data, the unsteady computational fluid dynamics calculation results are used in modeling. The obtained model can better simulate the swing motion of the underwater vehicle. Simulation and experimental results show a good consistency in free-fall tests during sea trials, as well as a prediction of the dive speed in the swing state.  相似文献   

宁波市城市土地利用绩效评价及障碍因子分析   总被引：1，自引：0，他引：1  

许珊  刘艳芳  彭明军  华梦丽 《地理信息世界》2017,24(3)

宁波市从2005年起围绕城市发展制定并开展了一系列"城中村改造"项目,积极完善城市土地利用模式,推动城市化进程。为探究这一时段宁波市城市土地利用绩效的变化,采用TOPSIS评价方法对城市土地利用绩效进行综合评价计算,并利用障碍度模型对宁波市城市土地利用绩效进行深入分析,指出日后城市土地利用重点。结果表明:①宁波市城市土地利用绩效指数逐步从0.059增长到1.000,绩效水平从"低级"达到"优质";②准则层指标障碍度不断变化,其中变化最大的为生态可持续,在2015年时降为0;③指标层障碍因子诊断结果说明地均从业人数等指标在持续、深层次地影响城市土地利用。  相似文献   

Relationship between geoacoustic properties and chemical content of submarine polymetallic crusts from offshore Brazil     

Arthur Ayres Neto  Vanessa Alves da Costa  Clara Pinto Ferreira Maia Porto  Thais Cristina Vargas Garrido  Jean-Pierre Hermand 《Marine Georesources & Geotechnology》2020,38(4):437-449

Abstract

Marine mining is the ocean’s new exploration frontier, and polymetallic crusts (PMCs) and ferromanganese nodules are considered a strategic resource for the future. Acoustic geophysical methods are a valuable tool for oceanic research and have been employed for several decades in the exploration of marine resources and environmental evaluations. The main objective of this work was to investigate the correlation between the chemical composition of PMCs from three different areas along the Brazilian continental margin and their physico-acoustic attributes (P-wave velocity, density and acoustic impedance). The results show that the geoacoustic properties of PMCs are correlated to their chemical composition. Measurements showed positive and negative trends between acoustic impedance and studied elements (Fe, Mn, Co, Cu, Zn, W and Ni) according to the direction of measurement, indicting high anisotropy levels. Our study sheds initial light on the correlation between acoustic properties and metal content of PMCs. The study facilitates assessments of the acoustic responses of PMCs allowing more efficient prospection and exploitation compared to ship-board geophysical techniques that are too qualitative to identify PMCs. The results can contribute to determining the best procedures and techniques for more efficient future exploration of this resource.  相似文献   

水声定位系统中迭代适应点分层的声线修正算法          下载免费PDF全文

陈嘉兴  赵晓旭  董怡靖  丁路  刘志华 《海洋科学》2023,47(4):155-164

水声定位系统中, 声线弯曲是造成定位误差大的主要原因, 本文针对该问题提出了一种迭代适应点分层(IAPL)的声线修正算法, 将声速剖面筛选分层修正声线。首先搭建水声定位模型, 通过拟合目标海域的监测数据, 得到声速高次函数; 其次探究声线弯曲时目标位置与掠射角的关联性, 由此构造出声线插值函数并求解路径参数; 最后提出划分原则, 精简声速剖面分层。仿真结果表明, 所提算法定位误差较低, 分层精简率均维持在48.04%的水平, 使计算量平均下降可达50.27%, 能够最大程度保留声速剖面的原始特征, 减少分层数量, 提高计算效率。  相似文献   

水下自动监测站的结构设计和试验     

李永军  李飞权 《海洋技术学报》2007,26(1):1-5

介绍了水下自动监测站的结构构成;围绕剖面测量功能的实现,论述了在总体设计、集成框架、浮动平台、驱传动系统、实时数据传输、剖面运动控制、试验和维护等方面应注意的主要问题以及采取的具体措施,供有关人员参考交流.  相似文献