The estimation of the thrust deduction fraction is generally conducted in ideal weather conditions. However, the presence of waves considerably alters the magnitude of this propulsive coefficient. The increased load of the propeller could be the main cause for the variation of the thrust deduction fraction in realistic operating conditions. In this work, load-varying self-propulsion model-scale numerical simulations in calm water conditions for the same ship speed are performed to investigate the influence of the propeller loading on the thrust deduction fraction. The single screw model-scale KVLCC2 tanker is selected as the case study. The results reveal a non-linear inverse correlation between the thrust deduction fraction and the propeller loading. A comparison with model-testing conducted on the KVLCC2 tanker in regular head waves suggests that the propeller loading is the main factor influencing the magnitude of the thrust deduction fraction in waves for the considered case vessel.
The results of load-varying self-propulsion model-scale experiments in calm water and regular deep-water following regular waves are presented. Open water tests were also performed at different propeller rotational speeds to evaluate the impact of the Reynolds number on the propeller thrust and torque. A model-scale fishing trawler was selected as the case study. Two ship speeds were considered. The open water curves showed a minimal influence of the Reynolds number on the thrust coefficient. However, the torque coefficient decreased with the increase of the Reynolds number. A good linear relationship between the tow force and the propeller thrust was detected in following waves and calm water conditions. The effective wake fraction increased in following waves compared to calm water conditions. The amplitude of the effective wake fraction decreased with the increase of the ship speed. A small influence of the ship motions and wave–particle velocities was reported on the thrust deduction fraction. The hull, relative rotative, propeller, and propulsive efficiency increased compared to calm water. The propulsive characteristics were estimated by considering the wave added resistance and the propulsive coefficients equal to their calm water values. Compared to the propulsive characteristics computed with the propulsive coefficients measured in waves, the propulsive efficiency was underestimated by about 2%–5%.
Driven by increased integration of renewable energy sources, the widespread decarbonization of power systems has led to energy price fluctuations that require greater adaptability and flexibility from grid users in order to maximize profits. Industrial loads equipped with flexible resources can optimize energy consumption rather than merely reacting to immediate events, thereby capitalizing on volatile energy prices. However, the absence of sufficient measured data in industrial processes limits the ability to fully harness this flexibility. To address this challenge, we present a black-box optimization model for optimizing the energy consumption of cooling systems in the aquaculture industry using Extreme Gradient Boosting (XGBoost) and Bayesian Optimization (BO). XGBoost is employed to establish a nonlinear relationship between cooling system power consumption and available measured data. Based on this model, Bayesian Optimization with the Lower Confidence Bound (LCB) acquisition function is used to determine the optimal discharge temperature of water into breeding pools, minimizing day-ahead electricity costs. The proposed approach is validated using real-world data from a case study at the Port of Hirtshals, Denmark based on measurements from 2023. Our findings illustrate that leveraging the inherent flexibility of industrial processes can yield financial benefits while providing valuable signals for grid operators to adjust consumption behaviors through appropriate price mechanisms. Furthermore, machine learning techniques prove effective in optimizing energy consumption for industries with limited measured data, delivering accurate and practical estimates.
Objective: To study enablers of bullying and harassment in the work environment on board ships.
Method: A qualitative sub-study embedded within a large population-based cross-sectional survey of the prevalence of bullying and harassment on ships in the Danish merchant fleet. The sub-study is based on in-depth semi-structured interviews and responses to open-ended questions in the survey questionnaire. In total, 32 participants were interviewed face-to-face or online. The data was imported into NVivo and coded thematically.
Results: Four themes emerged as enablers specific to the work environment on a ship: The first theme, Isolation, covers how the crew -as a group, is physically isolated from the world outside the vessel, but also that new crew members can be challenged when trying to become established inside the groups on board. The second theme, Hierarchy, encompasses how challenging the existing hierarchy based on rank is not tolerated and that the hierarchy is often maintained through bullying and harassment. The third theme, Crewing, includes how diversity related to e.g., culture, language, gender, or age/experience may create another form of hierarchy with the same negative consequences as the hierarchy based on formal rank. The fourth theme, Leadership, covers how leadership can enable both a good and an unacceptable work environment related to bullying and harassment. Conclusion: Bullying and harassment pose serious challenges to the work environment on ships. Four themes were identified as enablers of bullying and harassment. Some are a premise, but others may be improved through continued awareness and focused educational initiatives.
In this paper we extend the state-of-the-art stochastic programming models for the Maritime Fleet Renewal Problem (MFRP) to explicitly limit the risk of insolvency due to negative cash flows when making maritime shipping investments. This is achieved by modeling the payment of ships in a number of periodical installments rather than in a lump sum paid upfront, representing more closely the actual cash flows for a shipping company. Based on this, we propose two alternative risk control measures, where the first imposes that the cash flow in each time period is always higher than a desired threshold, while the second limits the Conditional Value-at-Risk. We test the two models on realistic test instances based on data from a shipping company. The computational study demonstrates how the two models can be used to assess the trade-offs between risk of insolvency and expected profits in the MFRP.
Background: Evidence on workplace safety and health promotion interventions shows that the
interventions have failed to demonstrate substantial benefits for seafarers. It is therefore important to explore what is the evidence of interventions with empowering elements regarding seafarers’ safety and health. This study aims to examine what is known about health promotion interventions in a maritime setting and whether they include an empowerment perspective. And secondly, what were the effects of these efforts. Methods: We systematically searched PubMed and NLM Gateway (for MEDLINE), Institute of Scientific Information/Web of Science (ISI/WOS), and SCOPUS up to July 2022 by using standard keywords including empowerment in the maritime setting. Data extraction was done by three independent reviewers. The quality of included studies was assessed by using the critical appraisal checklists from Joanna Briggs institute. Results: From 3313 studies initially identified, 10 articles met the inclusion criteria and were included in this review. Interventions covered a wide range of topics such as educational interventions on safety, first aid training, weight management, healthy eating, sexual harassment, alcohol abuse, and cancer prevention training. None of the studies applied a specific theory or definitions of empowerment
even though their aim was to increase seafarers’ empowerment in these areas. Conclusion: The studies focused on improving the safety and health status of the seafarers, however, they had no explicit focus on participation and empowerment. Increasing research with an empowerment approach in maritime sector is recommended to enhance the feasibility and
success of the programs in this hard-to-reach occupation.
Background: Evidence on workplace safety and health promotion interventions shows that the interventions have failed to demonstrate substantial benefits for seafarers. It is therefore important to explore what is the evidence of interventions with empowering elements regarding seafarers’ safety and health. This study aims to examine what is known about health promotion interventions in a maritime setting and whether they include an empowerment perspective. And secondly, what were the effects of these efforts. Methods: We systematically searched PubMed and NLM Gateway (for MEDLINE), Institute of Scientific Information/Web of Science (ISI/WOS), and SCOPUS up to July 2022 by using standard keywords including empowerment in the maritime setting. Data extraction was done by three independent reviewers. The quality of included studies was assessed by using the critical appraisal checklists from Joanna Briggs institute. Results: From 3313 studies initially identified, 10 articles met the inclusion criteria and were included in this review. Interventions covered a wide range of topics such as educational interventions on safety, first aid training, weight management, healthy eating, sexual harassment, alcohol abuse, and cancer prevention training. None of the studies applied a specific theory or definitions of empowerment even though their aim was to increase seafarers’ empowerment in these areas. Conclusion: The studies focused on improving the safety and health status of the seafarers, however, they had no explicit focus on participation and empowerment. Increasing research with an empowerment approach in maritime sector is recommended to enhance the feasibility and success of the programs in this hard-to-reach occupation. Systematic review registration number in PROSPERO: CRD42021260098.
Background: Fatigue is a concern in ferry shipping as it has a negative impact on crew members health and plays a major role in marine incidents and accidents. Research within land-based occupational settings has found that work-family conflict is an important risk factor for fatigue and that support from leaders constitutes a possible resource with the potential to buffer a negative impact from work-family conflict. Though, the working conditions of ferry shipping are likely to interfere with employee's family life those two factors have received little attention in research on seafarers' health. Therefore, the aim of this study was to investigate the direct associations between work-family conflict as well as leaders' support with fatigue in employees of the Danish ferry shipping industry. Further, the study aimed at testing whether support could buffer potential detrimental associations between work-family conflict and fatigue. Methods: The study design was cross-sectional, and 193 respondents answered to a self-administered questionnaire. Fatigue was measured with the Swedish Occupational Fatigue Inventory. Perceived work-family conflict and perceived supervisor support were assessed with two subscales from the Copenhagen Psychosocial Questionnaire. The association of potential risk factors with fatigue was determined using hierarchical multiple linear regression analyses. Results: After controlling for confounding, work-family conflict was found to be positively associated with four of the five subdimensions of fatigue; lack of energy, physical discomfort, lack of motivation and sleepiness, while more support from supervisors was related to less lack of energy, physical exhaustion and lack of motivation. Further, supervisor support was found to moderate the effect from work-family conflict on the physical subdimensions of fatigue. Conclusion: Although restricted by its cross-sectional design and a limited sample, this study provides support for the independent relevance of work family conflict and support from nearest superior for employee fatigue in ferry shipping. Further, there was evidence for a moderating role of such support on the negative impact of work-family conflict on the physical aspects of fatigue. Shipping companies may consider commencing initiatives which reduce conflicts between family life and work obligations, and that leader support may be a relevant component in such initiatives.
Background: Seafarers are at an increased risk of developing cardiovascular diseases (CVDs), potentially due to a stressful working environment and behavioral risk factors. To develop better prevention strategies, it is important to elucidate the extent of this risk. Therefore, we conducted a systematic literature review on CVD in seafarers. Method: We conducted systematic searches in five databases. All studies investigating CVDs among occupational seafarers, published in articles or conference papers, were eligible for inclusion. The identified records were screened and reviewed by two independent researchers, who also evaluated the methodological quality of the included studies. Results: Three thousand nine hundred and seventeen records qualified for screening, and 55 were eligible for inclusion. Most of the studies were observational, including cohort, frequency, incidence or prevalence studies, and review of case records. Around half were assessed at risk of biased findings. Participants in the studies were primarily from North America or the European continent and work onboard transportation vessels. Many studies investigated CVDs as a cause of death, focusing on conditions such as CVD, ischemic heart disease, and myocardial infarction. Frequency of CVD conditions varied but indicate that seafarers face a greater risk compared to the reference populations or control groups. Environmental factors were mainly investigated as risk factors. Conclusion: Our results indicate a higher risk of CVDs among seafarers compared to reference or control groups. However, due to the variable quality of the evidence, well-designed studies are needed to establish the causes of cardiovascular mortality and morbidity in seafarers and to investigate behavioral aspects of cardiovascular risk.
BACKGROUND: Fatigue is a recognised risk factor for safety in seafaring. While always dangerous, fatigue in ferry shipping is especially hazardous as it may jeopardise passengers' safety. To counteract fatigue, knowledge on its determinants is important. Little, however, is known on the influence from physical and psychosocial work environment factors within ferry shipping. The aim of the study was to investigate the association between work stress in terms of physical stressors, perceived job demands and job control and different dimensions of fatigue among ferry ship employees and to test whether a potential effect of work stress was mediated by sleep satisfaction. MATERIALS AND METHODS: The design was cross-sectional. 193 respondents answered to a self-administered questionnaire including standardised scales, i.e. the Swedish Occupational Fatigue Inventory and the Copenhagen Psychosocial Questionnaire for job demands and control. The association of risk factors with fatigue was determined using hierarchical multiple linear regression analyses. RESULTS: Physical work stressors were positively associated with only one of five fatigue subscales: lack of energy. Higher levels of demands were related to more lack of energy, lack of motivation, physical exertion and sleepiness, while more control was related to lesser lack of energy, lack of motivation and sleepiness. No demand-control interaction was found. Effects of demand and control were partly mediated by sleep satisfaction. CONCLUSIONS: Although limited by its cross-sectional design this study provides support for the independent relevance of demands and control for employee fatigue in ferry shipping and for a mediating role of sleep satisfaction.