Life Stage, Gender and Movement of Blue Crabs (Callinectes sapidus) in Lake Mattamuskeet and Connecting Canals

In their ranges on east and south coasts of the Americas as well as their established invasions in the Adriatic and Baltic,blue crabs,Callinectes sapidus,inhabit estuaries,sounds and coastal oceans and are commercially and ecologically important.How crabs move in response to physical variables is important to management.We monitored life stages at canal control structures,assessed gender ratios with recreational crabbing,learned from crabbers,and studied movements of tagged crabs in a canal connecting Lake Mattamuskeet to the Pamlico sound.Juveniles enter the lake through two of 4 canals connecting to the sounds.Females migrate out through one canal.The lake standing population is about 70% male.Movements of 240 crabs in August 2012 and 102 crabs in October 2014 were quantified using RFID tags with co-located meteorological and oceanographic devices.Non-spawning females and males are nomadic.Crabs released in the canal move in response to changes in water depth and go with the flow,toward the Pamlico Sound(summer 76% and fall 78%).What crabbers describe as a fall migration appears to be concentration of crabs in warmer deeper canals and then southern movement with flow generated by strong north winds.To be effective,management strategies like migratory corridors require understanding of crab movements.

A Review of the Calculation Methods of Lifting Capacity in Wind Loads on Ocean Platforms

Wind load is a control load that affects the safety of structures in the design of ocean platforms. It has not only direct and powerful effects that may cause structure resonance but also has indirect effects causing waves or currents in the ocean. By analyzing the domestic and international norms, this study presents a review of calculation methods of wind load on ocean platforms, which belongs to large-scale non-entity structure used in the open sea while surrounding wind has no fixed direction. Current computations according to the norms are not accurate, which even not takes the force of the wind against the surface perpendicular to the structure into consideration. Additionally, this study also introduces and compares the lift model of platforms based on different theories, such as vortex-excitation and vibration, engineering structure dynamics, gas flow pressure theory, analyzing their applicability, advantages, and disadvantages. This paper analyzes the limitations and applicable conditions of the existing calculation method itself, such as the lift model is suitable for the existence of stable vortex wake;the calculation method of the structural dynamics of marine engineering must be combined with the wind tunnel test and consider the mistakes caused by the position relationship;the numerical simulation method is accurate but tedious. This study provides an insight into the calculation methods of lift in designing ocean platforms, including the finite element method for simulating fluid force and updating formulas in Chinese norms.

A DEM investigation on simple shear behavior of dense granular assemblies

A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element method.Three series of numerical tests were performed to examine the effects of initial porosity,vertical stress and particle shape on simple shear behavior of the samples,respectively.It was found that during simple shear the directions of principal stress and principal strain increment rotate differently with shear strain level.The non-coaxiality between the two directions decreases with strain level and may greatly affect the shear behavior of the assemblies,especially their peak friction angles.The numerical modelling also reveals that the rotation of the principal direction of fabric anisotropy lags behind that of the major principal stress direction during simple shear,which is described as fabric hyteresis effect.The degrees of fabric and interparticle contact force anisotropies increase as particle angularity increases,whereas the orientations of these anisotropies have not been significantly influenced by particle shape.An extended stress–dilatancy relationship based on ROWE-DAVIS framework was proposed to consider the non-coaxiality effect under principal stress rotation.The model was validated by present numerical results as well as some published physical test and numerical modelled data.

DEM Modeling of Particle Breakage in Silica Sands under One-Dimensional Compression

A Discrete Element Method （DEM） model is developed to study the particle break- age effect on the one-dimensional compression behavior of silica sands. The ＇maximum tensile stress＇ breakage criterion considering multiple contacts is adopted to simulate the crushing of circular particles in the DEM. The model is compared with published experimental results. Com- parison between the compression curves obtained from the numerical and experimental results shows that the proposed method is very effective in studying the compression behavior of silica sands considering particle breakage. The evolution of compression curves at different stress levels is extensively studied using contact force distribution, variation of contact number and particle size distribution curve with loading. It is found that particle breakage has great impact on com- pression behavior of sand, particularly after the yield stress is reached and particle breakage starts. The crushing probability of particles is found to be macroscopically affected by stress level and particle size distribution curve, and microscopically related to the evolutions of contact force and coordination number. Once the soil becomes well-graded and the average coordination number is greater than 4 in two-dimension, the crushing probability of parent particles can reduce by up to 5/6. It is found that the average contact force does not always increase with loading, but increases to a peak value then decreases once the soil becomes more well-graded. It is found through the loading rate sensitivity analysis that the compression behavior of sand samples in the DEM is also affected by the loading rate. Higher yield stresses are obtained at higher loading rates.

The landscape of safety management systems research: A scientometric analysis

Safety management systems(SMSs)are widely applied across many industrial sectors,and a large body of liter-ature has been published addressing their design,implementation,effectiveness,and associated challenges.This article presents a high-level analysis of the SMS research domain,guided by a set of questions addressing the contents,structure,and evolution the research domain,its dominant themes and focus topics,the key scientific domains and journals contributing to its development,and the key publications serving as an intellectual basis for SMS related research.The results show a rapidly increasing volume of research outputs and a shift from re-search based in North America and Europe to Asia and Australia.There is only a limited number of institutions enduringly contributing to the field,and there are relatively few stable research collaborations,with the number of Chinese institutions publishing SMS related research fast expanding in recent years.The domain is strongly interdisciplinary and embedded in applied domains of science,with industrial engineering the most contribut-ing category,as well as categories focusing on the industrial application domains.A temporal evolution of the research activity in different application domains is apparent,with an initial focus on occupational health and safety,followed by process safety,patient safety,food safety,and construction safety.SMS research has a strong relation to safety culture and safety climate research,and while safety and risk management concepts and theo-ries form an important knowledge base for most application domains,the dominant views on accident causation differ between these.Research on SMS in the food industry is relatively separated from the other application domains.Based on the findings,various future research directions are discussed.

Light Scattering by Pure Water and Seawater: Recent Development

Light scattering by pure water and seawater is a fundamental optical property that plays a critical role in ocean optics and ocean color studies.We briefly review the theory of molecular scattering in liquid and electrolyte solutions and focus on the recent developments in modeling the effect of pressure,extending to extreme environments,and evaluating the effect of salinity on the depolarization ratio.We demonstrate how the modeling of seawater scattering can be applied to better understand spectral absorption and attenuation of pure water and seawater.We recommend future efforts should be directed at measuring the polarized components of scattering by pure water over a greater range of wavelengths,temperature,salinity,and pressure to constrain and validate the model and to improve our knowledge of the water’s depolarization ratio.

椭圆颗粒层理面定向对密实颗粒试样单剪力学特性的影响(英文)

目的:利用离散元数值模拟技术,从宏细观角度探究单剪受荷模式下,颗粒定向引起的层理面效应对数值试样强度与变形特征、应力-剪胀关系以及组构各向异性演化的影响及其机理。创新点:1.分析了单剪受荷条件下应力主轴偏转引发的主应力与主应变增量之间的非共轴效应,针对密实颗粒试样,研究了初始层理面倾角对非共轴应力-剪胀关系的影响;2.从细观力学角度,研究了应力主轴偏转条件下初始不同层理面试样的应力诱发组构各向异性特征,提出了一个可以考虑初始层理面效应的应力-接触力-组构经验关系式。方法:1.采用离散元团聚颗粒方法构建初始不同层理面定向的数值试样;2.采用傅里叶级数近似法对数值试样细观组构各向异性演化规律进行统计和定量数学分析;3.通过与已有文献数值模拟和室内试验结果的对比,探讨密实颗粒数值试样的单剪特性及非共轴应力-剪胀关系。结论:1.初始层理面定向显著影响数值试样的单剪强度与体变特征,且在定量上能与室内物理试验结果进行对比;2.在单剪受荷模式下,初始层理角越大,非共轴效应越显著;3.随着应力主轴的偏转,颗粒定向各向异性主方向逐渐趋于大主应力面作用方向,而接触法向各向异性的主方向基本垂直于颗粒定向各向异性主方向。4.本文提出的应力-接触力-组构关系式能够较好的反映颗粒定向对试样抗剪强度的影响。