Coming Soon to a Fjord Near You: Future Jellyfish Scenarios in a Changing Climate

Over the last decades, a dense population of the deep-sea/oceanic scyphozoan jellyfish Periphylla periphylla has established itself as top predator in the Trondheimsfjord in Norway, which has caused the traditional fisheries in this fjord to suffer. This was, however, not the first fjord this jellyfish invaded, and data suggest that it will not be the last one, either. With warmer temperatures, the jellyfish is moving northward in Norway, but not all fjords are created equal, and it is not thriving or taking up residence just anywhere. The current article explores three fjords in which Periphylla periphylla has become the top predator and outcompeted former ones. The main question of interest is why the jellyfish becomes dominant in one fjord and not another. The next question is which other Norwegian fjords further north exist with similar characteristics where we therefore would expect Periphylla periphylla to proliferate in the future. The latter is important from a policy and adaptation perspective for the local community of people, since the proliferation of the species unmistakably leads to fewer fish for commercial harvest and potentially less attractive waters for tourism purposes. Results show that three northern fjords, the Skjerstadfjorden the Holandsfjorden, and Stordjupna in the Vestfjord appear to be particularly vulnerable to a future Periphylla periphylla invasion.     

Ventilation of bottom water in the North Sea–Baltic Sea transition zone

The transition zone between the North Sea and the Baltic Sea is a highly dynamic region where a general estuarine circulation forms a regional scale frontal system from northern Kattegat to the Arkona Sea. This system is characterized by an upper low saline out?owing Baltic water mass from the in?owing saline Skagerrak bottom water to the Kattegat and Belt Sea area. Large and rapid ?uctuations of the frontal system are caused by barotropic transports, forced by changing sea level difference between northern Kattegat and the western Baltic Sea, and this results in high variability of the hydrographic conditions and also in frequent in- and out?ow events to the Baltic. The dynamics in the region are here analyzed by a regional model of the transition zone, covering the area from the northern Kattegat to the Arkona Sea. The model is validated against water level, temperature and salinity measurements from the region, and the transports through the Danish straits are related to previous estimates and empirical relations. A sensitivity study quantify the role of bathymetry, the tidally induced mixing and the in?owing Skagerrak bottom water for ventilating the bottom water with Skagerrak water or surface water.Furthermore, the dynamics in the region is analyzed with tracers representing the age of the water. The distribution of age tracers with different boundary conditions are analyzed, and the role of advection and mixing for ventilating the bottom water is quanti?ed in terms of the water age. It is shown that the Great Belt area is a very dynamical area where bottom water is ventilated with surface water. The interannual variation of the ventilation of bottom water in the period 2001–2003 is analyzed by various age tracers and related to observed oxygen conditions, and it is shown that the extreme hypoxic event in the autumn 2002 in the southern Kattegat, the Great Belt and in the western Baltic Sea coincide with an unusual low vertical ventilation rate in the Great Belt area, but normal advection rates of bottom water from the northern Kattegat. This indicates that during this particular event, and probably in general, ventilation of bottom water in the Great Belt has signi?cant in?uence on oxygen conditions in the southern part of the region and for ventilation of bottom waters in the western Baltic Sea. In contrast, the central Kattegat is primarily ventilated by advection of bottom water from the Skagerrak. An age tracer representing the ventilation rate of bottom water with either Skagerrak water or surface water is shown to be inversely correlated to the observed oxygen distribution in the region.     

Acceptance of disincentives to driving and pro-environmental transport intentions: the role of value structure,environmental beliefs and norm activation

Transportation - In order to facilitate pro-environmental transport mode use it is important to promote acceptance for disincentives to driving and intentions to use public transport. The present...     

Measurements of threshold values for incipient motion of sediment particles with two different erosion devices

For studies on sediment transport processes experimental data on the erosion behaviour of sediments are necessary. Because of significant differences in experimental setups and subsequently in resulting values comparisons and, where possible, correlations between methods are required. This study presents measurements with two different erosion devices (straight flume and microcosm erosion chamber), which were used for the determination of critical shear stress velocities for sandy submarine sediments and sieved sediment fractions. An approach is presented to convert measured current velocities into shear stress velocities via roughness length values and drag coefficients under hydrodynamically smooth and transitional turbulent flow conditions. The results from both devices show a good agreement and the measured erosion threshold values fit to established correlations between critical shear stress velocity and grain size. In the grain size range below 200 µm results for naturally composed sediments are influenced by effects caused by the silt- and clay fraction. Sieved sediment fractions in this grain size range tend to show lowered erosion thresholds in relation to the Shields' curve.     

Consistency in the development of performance assessment methods in the maritime domain

The maritime industry is considered to be a backbone of the global economy. It is therefore imperative to ensure that maritime operations run safely and efficiently. Assessment of maritime performance is necessary for designers and engineers to be able to pinpoint the weakest links in the system and make impactful system improvements. The current article presents a systematic quantitative literature review of research on performance assessment in the maritime industry with the goal of establishing an understanding of accuracy and consistency in the development of methods used to assess performance. The review focuses on four major segments within the industry—port logistics, ship handling, safety and environmental research—and investigates their uses in developing accurate and consistent performance assessment methods. After the completion of an exclusion process, 62 articles published in a wide range of academic journals were used in the analysis. Two important conclusions were drawn from the analysis. First, performance assessment is generally consistent throughout the maritime industry; most papers used accurate and consistent approaches to develop the methods (n?=?43). A subsequent bivariate analysis revealed a call for increased attention to the development of assessment methods within the maritime segment of ship handling. The current study suggests and discusses certain directions with regard to assessment research in the maritime industry.     

Wave analysis of porous geometry with linear resistance law

The wave diffraction-radiation problem of a porous geometry of arbitrary shape located in the free surface of a fluid is formulated by a set of integral equations, assuming a linear resistance law at the geometry. The linear forces, the energy relation and the mean horizontal drift force are evaluated for non-porous and porous geometries. A geometry of large porosity has an almost vanishing added mass. The exciting forces are a factor of 5–20 smaller compared to a solid geometry. In the long wave regime, the porous geometry significantly enhances both the damping and the mean drift force, where the latter grows linearly with the wavenumber. The calculated mean drift force on a porous hemisphere and a vertical truncated cylinder, relevant to the construction of fish cages, is compared to available published results.     

论安全文化如何应用于道路交通

近期研究表明,安全文化(特指交通安全文化)概念在改善交通安全方面极具潜力。然而,安全文化传统上适用于组织及其成员。探索安全文化在道路交通方面的应用,其核心问题是这一概念能够用于何种分析单元。重点探讨了三种选择:当地社区、国家和同类群体,并根据四个标准对其进行评估:1)如何定义;2)能否用于解释交通安全行为;3)是否具有影响交通安全行为的可能性;4)能否为交通安全问题提供新见解。得到的结论是:交通安全文化应用于当地社区和国家层面过于错综复杂,而应用于同类群体层面为进一步实施有针对性的交通安全改善措施提供了新的可行依据。最后指出需进一步研究的问题。     

Price formation of dry bulk carriers in the Chinese shipbuilding industry

In this paper, we present, for the first time, the price formation of Chinese dry bulk carriers based on the historical shipbuilding contract prices. Price determinants include generic market factors as well as Chinese elements. Principal component regression analysis is employed as the solution for the multicollinearity problem among explanatory variables. The result indicates that the time charter rate has the most significant positive impact on shipbuilding price; increases in three other factors, namely the cost of shipbuilding, the price-cost margin and the shipbuilding capacity utilisation, have positive influences in the descending order. Unlike the traditional perception of newbuilding price that shipbuilding cost has the most significant effect, we assert that the most important role the time charter rate plays is attributed mainly to the ‘China Factor’ in the bulk carrier sector. In addition, simulations are performed to investigate what would happen to the Chinese dry bulk carrier prices under changes in the time charter rate and shipbuilding cost. The findings are useful for Chinese shipyards, shipowners and emerging shipbuilders.     

Factors that promote innovation in shipping companies

This study seeks to identify factors that promote innovation in shipping companies. The study is based on an empirical investigation of 63 companies headquartered in Norway. The results imply that organizational and interorganizational variables are important to innovation. Three aspects of innovation are focused on: (1) service/product innovations, (2) market innovations, and (3) production method innovations. The explanatory variables that are applied in this study capture between 13–51% of the variability of the measures of innovation. The results indicate that an explicit strategy that promotes innovation is very important for the actual level of innovation within shipping companies. In management literature, it is often assumed that organic organizational features like decentralized decision-making promote innovation. The opposite features are assumed to restrain innovation. However, the results do not support these basic assumptions. For example, it seems to be important that managers make precise decisions in order to promote innovation.     

Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres

ABSTRACT

Stability control of a vehicle in autonomous safety-critical at-the-limit manoeuvres is analysed from the perspective of lane keeping or lane changing, rather than that of yaw control as in traditional ESC systems. An optimal control formulation is developed, where the optimisation criterion is a linear combination of the initial and final velocity of the manoeuvre. Varying the interpolation parameter in this formulation turns out to result in an interesting family of optimal braking and steering patterns in stabilising manoeuvres. The two different strategies of optimal lane-keeping control and optimal yaw control are shown to be embedded in the formulation and result from the boundary values of the parameter. The results provide new insights and have the potential to be used for future safety systems that adapt the level of braking to the situation at hand, which is demonstrated through examples of how to exploit theresults.