SCUBA Diver Specialization and Behavior Norms at Coral Reefs

SCUBA diving is an increasingly popular activity that provides a number of benefits to coastal communities. However, the sustainability of recreational diving on coral reefs is largely dependent on the health of reef ecosystems. Divers can minimize their impacts to coral reefs through responsible diving behaviors, which are in part guided by social norms. The behavioral obligation and sanction components of twelve diving behaviors were determined for Florida Keys divers throughout the course of a year. Recognizing that recreationists are not homogenous, these norms were compared according to diver specialization level. Specialized divers felt a stronger obligation not to touch corals and to pick up garbage from the sea floor than did less specialized divers. Specialized divers also reported they would feel greater embarrassment for losing buoyancy control, touching corals, taking pieces of dead corals, or touching marine mammals. The findings point to a connection between specialization level and social norms, and a relationship to ensuring continued reef health.     

Co-operation and competition in international container transport: strategies for ports

This paper focuses on the response of port authorities to the changing market environment in which they operate. It documents the changes taking place in the relationships between port authorities and terminal management companies and considers the strategic issues faced by these groups and other port interests. In particular, it investigates the potential conflicts of interest for a port authority in matters related to the level of competition amongst terminals within a port and the amount of competition amongst ports.     

The sensitivity of parameter estimates to data specification in mode choice models

Standard network data are generally used in estimation of mode choice models. These data are inaccurate in several ways, but the cost of correcting the inaccuracies is great. This paper analyzes the effects which correcting some of the inaccuracies in the standard network data has on the estimated parameters of mode choice models. Models are estimated on the standard network data and on data which have been adjusted so as to correct the problems in the standard network data. It is found that, for analysis of policies affecting transfer wait times or distances to bus stops, correction of the standard network data is advisable. For other policy analyses, however, it seems that the extra expense of correcting the standard data is unnecessary.     

Decoupled robust control of vehicular platoon with identical controller and rigid information flow

Platoon driving has potential to significantly benefit road traffic. This study presents a decoupled robust control strategy for a vehicular platoon with identical feedback controller and rigid information topology. The node dynamics of vehicle with a lower-level controller is assumed to be covered by a multiplicative uncertainty model. The vehicular platoon control system is skillfully decomposed into an uncertain part and a diagonal system by applying linear transformation and eigenvalue decomposition on information flow graph. Then the requirements of robust stability and distance tracking error are equivalent to the H-infinity norm of decoupled sub-systems. Comparative simulations with a non-robust controller and different communication topologies are conducted to demonstrate the robust stability and distance tracking performances of the proposed method.     

The design of single allocation incomplete hub networks

The hub location problem deals with finding the location of hub facilities and allocating the demand nodes to these hub facilities so as to effectively route the demand between any origin–destination pair. In the extensive literature on this challenging network design problem, it has widely been assumed that the subgraph induced by the hub nodes is complete. Relaxation of this basic assumption constitutes the starting point of the present work. In this study, we provide a uniform modeling treatment to all the single allocation variants of the existing hub location problems, under the incomplete hub network design. No network structure other than connectivity is imposed on the induced hub network. Within this context, the single allocation incomplete p-hub median, the incomplete hub location with fixed costs, the incomplete hub covering, and the incomplete p-hub center network design problems are defined, and efficient mathematical formulations for these problems with O(n³) variables are introduced. Computational analyses with these formulations are presented on the various instances of the CAB data set and on the Turkish network.     

复杂悬跨条件下的管线涡激振动分析(英文)

Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections, but also generates vortex induced vibration (VIV), which can lead to fatigue issues. The phenomenon, if not predicted and controlled properly, will negatively affect pipeline integrity, leading to expensive remediation and intervention work. Span analysis can be complicated by: long span lengths, a large number of spans caused by a rough seabed, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a .state-of-the-art. finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation.     

Maritime security and seafarers’ welfare: Towards harmonization

This article examines the negative situation surrounding seafarers’ welfare in the post 9–11 shipping world. Its main focus is the denial of shore leave which has become a prime source of disharmony since the implementation of post 9–11 security measures. It discusses the implementation of these measures which has been at the expense of seafarers’ customary right to shore leave.     

Fatigue analysis of butt welded AH36 steel joints: Thermographic Method and design S–N curve

The traditional methods of fatigue assessment of welded joints have some limitations, and are extremely time consuming. In order to overcome these difficulties, the Thermographic Method (TM), based on thermographic analyses, has been applied to predict the fatigue behaviour of butt welded joints, made of AH36 steel, largely used in shipbuilding. Experimental tests have been carried out to assess the fatigue capability in terms of S–N curves and fatigue limits. The predictions of the fatigue capability obtained resorting to the Thermographic Method show a good agreement with those derived from the traditional procedure. Moreover, the fatigue design recommendations were compared to the experimental data in order to analyse the reliability of the codes.     

Habitat characteristics as determinant of the structure and spatial distribution of epibenthic and demersal communities of Le Danois Bank (Cantabrian Sea, N. Spain)

The purpose of this paper is to detect and describe general trends in the spatial distribution of epibenthic and demersal communities of Le Danois Bank (El Cachucho) in relation to the environmental variables that characterize their habitat by means of multivariate ordination. Data were derived from two multidisciplinary surveys carried out in October 2003 and April 2004 included in the ECOMARG project. The surveys were focused on the study of the physical scenario, including both geological (seabed characterization from bathymetry and backscatter data) and hydrographic features, and the different compartments of the benthic fauna (endobenthic, epibenthic, suprabenthic and demersal communities). For the present study, epibenthos and demersal species were sampled using two different gears, a 3.5 m beam trawl and a Porcupine 39/52 type baca otter trawl respectively. The total species richness combining both samplers ascended to 221, including 71 species of fishes, 65 crustaceans, 35 molluscs, 29 echinoderms, 10 cnidarians and 5 sponges.Multivariate methods were used for the study of the characteristics of communities and habitats. Hierarchical cluster analysis was applied to calculate and visualize similarities between samples in terms of species composition. To assess the amount of variation of faunal densities related to a set of eight environmental variables, a redundancy analysis (RDA) was used. The set of environmental variables used were: depth, near-bottom temperature and salinity, sedimentary typology (dry weight percentages of coarse sands, medium and fine sands, silt and organic matter) and seafloor reflectivity. Using the spatial distribution of the ranges of depth and seafloor reflectivity that characterize the habitats of the faunal assemblages we defined the spatial distribution of the different communities.The multivariate analysis of 18 beam-trawl samples and 15 otter trawl samples showed the existence of 4 main assemblages associated with the more characteristic habitats of the area. The Callogorgia–Chimaera community live mainly in the areas at the top of the Bank (425–550 m depth), where the sediment coverage is lower and there exists a high presence of rocky outcrops. The Gryphus–Galeus community were found in the areas at the top of the Bank covered by medium and fine sand sediments with low organic matter content. The Phormosoma–Trachyrincus community live on the sedimentary terraces that characterize the Bank break (550–800 m) and the Pheronema–Deania community occupy all the deeper (800–1050 m) sedimentary grounds of the inner basin.     

Remotely-sensed chlorophyll a observations of the northern Red Sea indicate seasonal variability and influence of coastal reefs

The biological dynamics of the open northern Red Sea (21.5°–27.5° N, 33.5°–40° E) have not been studied extensively, due in part to both the inaccessibility of this desert region and political considerations. Remotely-sensed chlorophyll a data therefore provide a framework to investigate the primary patterns of biological activity in this oceanic basin. Monthly chlorophyll a data from the 8-year Sea-viewing Wide Field-of-View sensor (SeaWiFS) mission, and data from the Moderate Resolution Imaging Spectroradiometer (MODIS), were analyzed with the Goddard Earth Sciences Data and Information Services Center (GES DISC) online data analysis system “Giovanni”. The data indicate that despite the normal low chlorophyll a concentrations (0.1–0.2 mg m^− 3) in these oligotrophic waters, there is a characteristic seasonal bloom in March–April in the northernmost open Red Sea (24° to 27.5° N) concurrent with minimum sea surface temperature. The location of the highest chlorophyll concentrations is consistent with a linear box model [Eshel, G., and Naik, N.H., 1997. Climatological coastal jet collision, intermediate water formation, and the general circulation of the Red Sea. J. Phys. Oceanogr. 27(7), 1233–1257.] of Red Sea circulation. Two years in the data set exhibited a different seasonal cycle consisting of a relatively weak northern spring bloom and elevated chlorophyll concentrations to the south (21.5° to 24° N).The data also indicate that large coral reef complexes may be sources of either nutrients or chlorophyll-rich detritus and sediment, enhancing chlorophyll a concentration in waters adjacent to the reefs.