“Seafarers should be navigating by the stars”: barriers to usability in ship bridge design

Cognition, Technology & Work - Navigating a ship is a complex task that requires close interaction between navigators and technology available on the ship’s bridge. The quality of this...     

Numerical collapse analysis of compression members

A brief survey of weld-induced stresses and deflections in steel-plated structures is given. A finite element approach for analyzing stiffened panels is presented. The stiffener formulation accounts for torsional buckling. Yielding is taken into account and, based on the updated Lagrangian formulation, the effect of large deflections is allowed for. By using the so-called volume approach the development of plastic zones can be followed. The non-linear equations are solved using a combined step-iterative procedure.The examples presented comprise an unstiffened rectangular plate under biaxial compression, and two stiffened panels under uniaxial compression. The effect of initial deflections and stresses is considered.     

Matching policy and people? Household responses to the promotion of renewable electricity

In this paper, we study the responses among households to the promotion of renewable electricity. We analyse an experiment conducted by a Norwegian power company that offered Guarantees of Origin of supply to 5,000 of their customers. In the experiment, five different groups of 1,000 customers each received information about a renewable electricity certificate and how to purchase it. The information and the reasons given for why the customers should accept the offer was framed differently to each of the groups. The experiment produced minimal responses, and we use material from focus group discussions and in-depth interviews for interpreting and explaining the results. The analysis shows that customers tend to disregard information coming from their supplier, while there is also a low degree of commensurability between the message presented in the information and the understandings and perceptions held by the customers. For example, whereas the information contained the argument that customers must purchase certificates to obtain renewable electricity, Norwegians, because of their awareness of the country’s hydro-based production system, perceive electricity to be renewable as it is. Additionally, focus group participants found the presented terms and figures to be incomprehensible to the extent that the information can be said to have produced ignorance in them. In turn, this negatively affected people’s trust in the message and also its sender, as relevance and reliability are disclosure’s main challenges in Norway. We use the case of electricity labelling in Norway to demonstrate some of the general challenges associated with using information as a tool for changing people’s consumption patterns in deregulated energy markets.     

Latitudinal distribution of persistent organic pollutants in pelagic and demersal marine fish on the Norwegian Coast

The latitudinal distribution of persistent organic pollutants (POPs: legacy organochlorines [OCs], polybrominated diphenyl ethers [PBDEs,] and hexabromocyclododecane [HBCD]) was examined in livers of two species of marine fish, the pelagic saithe (Pollachius virens,n = 40) and the demersal cod (Gadus morhua,n = 40), along a south-north gradient (59°-70°N) on the Norwegian Coast. Cod had in general two to three times higher concentrations of POPs than saithe, probably because of higher exposure in the benthic food chain. The concentrations of heavy halogenated compounds were higher in the southernmost region than further north. Moreover, the POP pattern showed a gradual shift in the compositions from south to north, especially for OCs in cod: i.e. the relative importance of low-chlorinated polychlorinated biphenyl (PCB) congeners and some OC-pesticides (e.g., hexachlorobenzen [HCB]) in the contaminant burdens increased with latitude. The latitudinal fractionation signal was weaker in saithe, possibly due to its pelagic and nomadic behavior. Hence, this study shows not only a strong latitudinal fractionation in the compositional patterns of POPs in marine fish but also the effects of habitat use and fish behavior.     

Dynamic response analysis of wind turbines under blade pitch system fault,grid loss,and shutdown events

This study focuses on the dynamic responses of land‐based and floating wind turbines under blade pitch system fault and emergency shutdown conditions. The NREL 5 MW turbine is studied. A hydraulic pitch system is considered, and the faults under study are events with a seized blade or a blade running out of control. Emergency shutdown is defined as a fast pitch‐to‐feather maneuver of the blades. Load cases with power production and grid fault with ensuing shutdown are also analysed for comparison. The fault scenarios and the blades' fast pitching activity are simulated using HAWC2 through external Dynamic Link Libraries. On the basis of the time‐domain simulations, the response characteristics of the land‐based and the floating turbines in the four design load cases are compared. The load effects from the fault conditions are compared with the operational cases. Strong system dynamics and resonant responses, such as the tower elastic mode and the yaw resonant response, are elicited during shutdown. If the pitch system has a fault and one blade is hindered from normal pitching, the uneven load distribution of the blades leads to large structural and motion responses. For both turbines, the response maxima vary cyclically with the instantaneous azimuth when the blades start pitching to feather. For the floating wind turbine, the interaction of waves and wind also affects the results. The effect of the pitch rate during shutdown is analysed. The responses of the land‐based turbine in grid loss and shutdown conditions are proportional to the pitch rate, whereas decreased sensitivity is found in the cases with pitch system faults. For the floating turbine, the effect of the pitch rate is small, and reduced pitch and yaw motion extremes are observed as the pitch rate increases. Copyright © 2013 John Wiley & Sons, Ltd.     

Short‐term extreme response analysis of a jacket supporting an offshore wind turbine

Wind turbines must be designed in such a way that they can survive in extreme environmental conditions. Therefore, it is important to accurately estimate the extreme design loads. This paper deals with a recently proposed method for obtaining short‐term extreme values for the dynamic responses of offshore fixed wind turbines. The 5 MW NREL wind turbine is mounted on a jacket structure (92 m high) at a water depth of 70 m at a northern offshore site in the North Sea. The hub height is 67 m above tower base or top of the jacket, i.e. 89 m above mean water level. The turbine response is numerically obtained by using the aerodynamic software HAWC2 and the hydrodynamic software USFOS . Two critical responses are discussed, the base shear force and the bending moment at the bottom of the jacket. The extreme structural responses are considered for wave‐induced and wind‐induced loads for a 100 year return‐period harsh metocean condition with a 14.0 m significant wave height, a 16 s peak spectral period, a 50 m s ^{? 1} (10 min average) wind speed (at the hub) and a turbulence intensity of 0.1 for a parked wind turbine. After performing the 10 min nonlinear dynamic simulations, a recently proposed extrapolation method is used for obtaining the extreme values of those responses over a period of 3 h. The sensitivity of the extremes to sample size is also studied. The extreme value statistics are estimated from the empirical mean upcrossing rates. This method together with other frequently used methods (i.e. the Weibull tail method and the global maxima method) is compared with the 3 h extreme values obtained directly from the time‐domain simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Fluctuating wing asymmetry and hepatic concentrations of persistent organic pollutants are associated in European shag (Phalacrocorax aristotelis) chicks

In aquatic birds, high body burdens of persistent organic pollutants (POPs) have been associated with developmental effects related to growth, increased fluctuating wing asymmetry, and disruption of the thyroid hormone, vitamin A (retinol) and vitamin E (tocopherol) homeostasis. The aim of the present study was to examine if morphological variables (body mass, liver mass, wing length, tarsus length and head length), fluctuating asymmetry of the wings and tarsus, growth rates and endocrine variables (thyroid hormones, retinol and tocopherol) were associated with hepatic levels of POPs (PCBs, OCPs and PBDEs) in 21 day old chicks of European shag (Phalacrocorax aristotelis). Partial Least Squares (PLS) analysis showed that fluctuating asymmetry of wing bone length (FA_WBL) was affected by PCB-105, -118, -138, -153, and -180 (r²x = 0.88, r²y = 0.35, q² = 0.29). Bivariate correlation confirmed significant positive relationships between FA_WBL and each of these PCB congeners. In the PLS model no other biological variables were significantly affected by any of the POPs. Levels of POPs were much lower in the shag chicks than in eggs and in hatchlings from the same breeding colony, most likely due to growth dilution of the compounds. We suggest that the effects of the PCBs on FA_WBL may be due to effects of these compounds on bone growth and bone structure. FA_WBL may have functional effects on the fitness if it persists after fledging.     

Response analysis and comparison of a spar‐type floating offshore wind turbine and an onshore wind turbine under blade pitch controller faults

This paper analyses the effects of three pitch system faults on two classes of wind turbines, one is an onshore type and the other a floating offshore spar‐type wind turbine. A stuck blade pitch actuator, a fixed value fault and a bias fault in the blade pitch sensor are considered. The effects of these faults are investigated using short‐term extreme response analysis with the HAWC2 simulation tool. The main objectives of the paper are to investigate how the different faults affect the performance of wind turbines and which differences exist in the structural responses between onshore and floating offshore wind turbines. Several load cases are covered in a statistical analysis to show the effects of faults at different wind speeds and fault amplitudes. The severity of individual faults is categorized by the extreme values the faults have on structural loads. A pitch sensor stuck is determined as being the most severe case. Comparison between the effects on floating offshore and onshore wind turbines show that in the onshore case the tower, the yaw bearing and the shaft are subjected to the highest risk, whereas in the offshore case, the shaft is in this position. Copyright © 2014 John Wiley & Sons, Ltd.