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- Li, Zhiyuan, 1974, et al.
(author)
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Fatigue damage assessment of container ships concerning wave-induced torsion
- 2010
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In: Proceedings of the ASME 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) in Shanghai, China, June 6-11, 2010. - 9780791849101
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Conference paper (peer-reviewed)abstract
- The traditional method to assess fatigue damage of ship structures assumes moderate wave amplitudes and linear responses. This method can be questioned when applied on container ships that are characterized by large deck openings, because the low torsion rigidity of this type of ship makes it sensitive to oblique waves. In this paper, the 3D hydrodynamic code WASIM is used to simulate a 4400 TEU container ship operating in the North Atlantic Ocean. Nonlinear wave loads are utilized for direct calculation of the stress histories under severe sea states. The warping stress from wave-induced torsion is separated from the stress components from vertical and horizontal bending. The contribution to fatigue damage accumulation from warping stresses is evaluated. For comparison, the results from the numerical simulations and fatigue calculations are verified with full-scale measurements made on a similar type of container vessel.
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| 4. |
- Styhre, Alexander, 1971, et al.
(author)
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Managing knowledge in platforms: boundary objects and stocks and flows of knowledge
- 2010
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In: Construction Management and Economics. - : Informa UK Limited. - 1466-433X .- 0144-6193. ; 28:6, s. 589-599
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Journal article (peer-reviewed)abstract
- Previous research suggests that construction industry companies use relatively little formal managerial procedures when managing knowledge. Instead, many construction companies are relying on informal networks and social capital as conduits for the sharing of knowledge. However, objects play an important role in organizations as vehicles for the sharing of knowledge. The use of platforms, standardized packages of prescribed components, routines and practices, in a major Scandinavian construction company (SCC), demonstrates that platforms are potentially useful when sharing and accumulating knowledge. The platform concept is a boundary object integrating various functions and activities and standardizing work procedures while at the same time leaving some room for contingencies and local conditions. SCC’s use of platforms contributes to the understanding of knowledge sharing practices by emphasizing the role of formally enacted objects and tools and by underlining the need for bridging and bonding the stocks and flows of knowledge in construction companies.
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- Forssén, Jens, 1968, et al.
(author)
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Wind Turbine Noise Propagation over Flat Ground: Measurements and Predictions
- 2010
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In: Acta Acustica united with Acustica. - Stuttgart : S. Hirzel Verlag. - 1610-1928 .- 1861-9959. ; 96:4, s. 753-760(8)
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Journal article (peer-reviewed)abstract
- Noise from wind turbines is of concern in the planning process of new wind farms, and accurate estimations of immission noise levels at residents nearby are required. Sound propagation from wind turbine to receiver could be modelled by a simplified standard model assuming constant meteorological conditions, by an engineering method taking atmospheric and ground propagation conditions into account, or by a more exact model. Epidemiological studies have found a higher frequency of annoyance due to wind turbine noise than to other community noise sources at equal noise levels, indicating that the often used simplified model is not sufficient. This paper evaluates the variation of immission sound levels under the influence of meteorological variation and explores if the prediction of levels could be improved by taking the effect of wind speed on sound propagation into account. Long-term sound recordings and measurements at a distance of 530 m from a wind turbine show that the simplified standard model predicts the average sound pressure levels satisfactorily under downwind conditions, and that a more complex propagation model might not be needed for wind turbine noise at a relatively short distance. Large variations of sound immission levels at the same wind speed were however present. Statistical analysis revealed that these variations were influenced by meteorological parameters, such as temperature, static pressure and deviation from ideal downwind direction. The overall results indicate that meteorological factors influence the noise generated by the wind turbine rather than the sound propagation.
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- Löfhede, Johan, 1978, et al.
(author)
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Automatic classification of background EEG activity in healthy and sick neonates
- 2010
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In: Journal of Neural Engineering. - : IOP Publishing. - 1741-2560 .- 1741-2552. ; 7:1
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Journal article (peer-reviewed)abstract
- The overall aim of our research is to develop methods for a monitoring system to be used at neonatal intensive care units. When monitoring a baby, a range of different types of background activity needs to be considered. In this work, we have developed a scheme for automatic classification of background EEG activity in newborn babies. EEG from six full-term babies who were displaying a burst suppression pattern while suffering from the after-effects of asphyxia during birth was included along with EEG from 20 full-term healthy newborn babies. The signals from the healthy babies were divided into four behavioural states: active awake, quiet awake, active sleep and quiet sleep. By using a number of features extracted from the EEG together with Fisher’s linear discriminant classifier we have managed to achieve 100% correct classification when separating burst suppression EEG from all four healthy EEG types and 93% true positive classification when separating quiet sleep from the other types. The other three sleep stages could not be classified. When the pathological burst suppression pattern was detected, the analysis was taken one step further and the signal was segmented into burst and suppression, allowing clinically relevant parameters such as suppression length and burst suppression ratio to be calculated. The segmentation of the burst suppression EEG works well, with a probability of error around 4%.
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- Mao, Wengang, 1980, et al.
(author)
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The effect of whipping/springing on fatigue damage and extreme response of ship structures
- 2010
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In: Proceedings of the ASME 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) in Shanghai, China, June 6-11, 2010. - 9780791849101 ; 2
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Conference paper (peer-reviewed)abstract
- Wave-induced vibrations, also known as whipping and springing, are defined as high frequency response of ship structures. In this paper, the fatigue damage caused by whipping and springing is presented by investigating the amidships section of a 2800 TEU container ship that operates in the North Atlantic Ocean. A simplified fatigue model, originally from the generalized narrow-band approximation for Gaussian load, is employed to include the damage contribution from wave-induced vibrations. In this model, the significant response range hs and the mean stress up-crossing frequency fz are simplified using only the wave-induced loading and encountered wave frequency, respectively. The capacity and accuracy of the model is illustrated by application on the measurements of the 2800 TEU container ship for different voyages during 2008. The whipping-induced contribution to the extreme response is investigated by means of the level crossing approach. It shows that the level crossing model for Gaussian load cannot be used for the prediction of extreme responses, such as the 100-year stress, based on a half-year full-scale measurement. It is found that a more complicated non-Gaussian model is required to consider the contribution from whipping.
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- Rosen, Lars, 1962, et al.
(author)
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Comparing risk-reduction measures to reach water safety targets using an integrated fault tree model
- 2010
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In: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749. ; 10:3, s. 428-436
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Journal article (peer-reviewed)abstract
- In the third edition of the Guidelines for Drinking-water Quality, the World Health Organization concludes that an integrated management of risks in source waters, treatment systems and distribution networks is the most effective way to guarantee safe drinking water to consumers. The integrated approach is fundamental to avoid sub-optimisation of risk-reduction measures. This paper presents an application of an integrated and quantitative risk model for comparing risk-reduction measures to support decisions for reaching specified water safety targets. A fault tree approach is used for structuring the risk analysis and for estimating the risk, expressed as Customer Minutes Lost (CML). Input information is a combination of hard data and expert judgements. Uncertainties in input information are considerable and modelled by a Bayesianstatistical approach. A drinking water system in Sweden is used to exemplify model application. Quantitative safety targets have been confirmed at the political level as a basis for long-term planning of investments and reinvestments. One target defines an acceptable risk level of 144 annual CML for the average consumer. For the current system structure an estimated risk of 612CML was obtained. Four risk-reduction alternatives were compared and they reduce the risk to between 50 and 81 CML, i.e. below the acceptable level. The paper describes how a structuredand thorough analysis of risk-reduction measures can facilitate transparency and long-term planning of drinking water systems.
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| 10. |
- Sandsjö, Leif, 1958, et al.
(author)
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Clinical evaluation of a myofeedback-based teletreatment service applied in the workplace: a randomized controlled trial
- 2010
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In: Journal of Telemedicine and Telecare. - : SAGE Publications. - 1357-633X .- 1758-1109. ; 16:6, s. 329-335
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Journal article (peer-reviewed)abstract
- We evaluated the clinical effects of a myofeedback-based teletreatment service in terms of pain, pain-related disability and work ability. We also investigated the time investment/ savings of this treatment with respect to conventional care. Sixtyfive women with neck and shoulder pain at work participated in the study. Thirty-three took part in the teletreatment and 32 participated in a control group which continued with conventional care. Questionnaires were completed before the start of the intervention (baseline) and at initial follow-up (T0) and 3 months (T3) after the intervention ended. A general linear model analysis for repeated measurements showed an improvement in terms of pain and work ability for both groups taken together, with no differences between them. Non-parametric tests showed an intervention effect in painrelated disability for both groups together and no differences between them when tested at baseline, T0 and T3. The time saved in relation to conventional care was mainly from reduced travel time, which was 41 min per teleconsultation. The teletreatment service allowed employees to take part in muscle relaxation training while performing their regular work. The clinical evaluation showed that the treatment was on par with conventional care, but without the effort and time loss associated with regular visits to the clinic. We conclude that the myofeedback-based teletreatment service has potential for addressing neck and shoulder symptoms at the workplace.
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