This paper addresses the fleet renewal problem and particularly the treatment of uncertainty in the maritime case. A stochastic programming model for the maritime fleet renewal problem is presented. The main contribution is that of assessing whether or not better decisions can be achieved by using stochastic programming rather than employing a deterministic model and using average data. Elements increasing the relevance of uncertainty are also investigated. Tests performed on the case of Wallenius Wilhelmsen Logistics, a major liner shipping company, show that solutions to the model we present perform noticeably better than solutions obtained using average values.
Ship collision with offshore installations is one of the key concerns in design and assess of platforms performance and safety. This paper presents an analysis on collision energy and structural damage in ship and offshore platform collisions for various collision scenarios. The platform or rig is treated as either rigid or flexible and its sensitivity on collision energy and structural damage is studied. An application example where an ice-strengthened supply vessel collides against a jack-up rig is analysed and the crushing resistance of the involved thin-walled structures is evaluated.
The impact of climate change in the Arctic Ocean such as ice melting and ice retreat facilitates natural resources extraction. Arctic fossil fuel becomes the drivers of geopolitical changes in the Arctic Ocean. Climate change facilitates natural resource extractions and increases competition between states and can result in tensions, even military ones. This article investigates through a political and legal analysis the role of China as an emerging regulatory sea power in the Arctic Ocean given its assertive “energy hungry country behaviour” in the Arctic Ocean. The United Nations Convention on the Law of the Sea (UNCLOS) and the Arctic Council (AC) are taken into consideration under climate change effects, to assess how global legal frameworks and institutions can deal with China’s strategy in the Arctic Ocean. China’s is moving away from its role as “humble power” to one of “informal imperialistic” resulting in substantial impact on the Arctic and Antartic dynamism. Due to ice-melting, an easy access to natural resources, China’s Arctic strategy in the Arctic Ocean has reinforced its military martitime strategy and has profoundly changed its maritime military doctrine shifting from regional to global in the context of UNCLOS. In particular, it is wondered, what China understands about the public order dimension of UNCLOS. The article concludes that despite China’ assertive behaviour towards the Arctic environmental ocean and its rise as global sea power, for the time being, China cannot be considered as a variable for Arctic security as there are no sufficient legal and policy objective elements to adduct that it constitutes a threat to Artic ocean security.
Maritime security is one of the latest buzzwords of international relations. Major actors have started to include maritime security in their mandate or reframed their work in such terms. Maritime security is a term that draws attention to new challenges and rallies support for tackling these. Yet, no international consensus over the definition of maritime security has emerged. Buzzwords allow for the international coordination of actions, in the absence of consensus. These, however, also face the constant risk that disagreements and political conflict are camouflaged. Since there are little prospects of defining maritime security once and for all, frameworks by which one can identify commonalities and disagreements are needed. This article proposes three of such frameworks. Maritime security can first be understood in a matrix of its relation to other concepts, such as marine safety, seapower, blue economy and resilience. Second, the securitization framework allows to study how maritime threats are made and which divergent political claims these entail in order to uncover political interests and divergent ideologies. Third, security practice theory enables the study of what actors actually do when they claim to enhance maritime security. Together these frameworks allow for the mapping of maritime security.
Short-term variability of ship responses is investigated by cross-spectrum analysis. In a steady state condition, it is well known that a certain length of sampled data is required for stable results of the spectral analysis. However, the phase lag between responses, in terms of the phase angle of the cross-spectra, has not been discussed in detail. Using long stationary time series, the transition of amplitudes and relative phase angles of the cross-spectra has
been investigated by iterative analyzes with a few seconds of time shifting. In the results, the short-term variability of the relative phase angle was observed. In effect, the variability may compromise the accuracy of the wave buoy analogy.
ABSTRACT: This article reviews early experiences with what is commonly referred to as 'regionalisation'. Initially, the article briefly recalls the shortcomings of the traditional, highly centralized governance structure of the Common Fisheries Policy of the European Union, for which regionalization was widely perceived as a solution, while at the same time providing an overview of the policy processes and various inputs that led to the provisions of recent regulation. Subsequently, the article presents empirical experiences related to the actual implementation and performance of the regional structures in the North and Baltic Seas and discusses the extent to which the adopted model of regionalization is appropriate in light of the objectives it was intended to advance. Finally, the article offers some scenarios of possible 'futures' of the regional structures.
Slugging flow in offshore oil & gas multi-phase transportation pipelines cause big challenges as the flow regime induces flow and pressure oscillations in the multi-phase pipelines. The negative impacts of the most severe slugs are significant and thus the elimination of slugging flow in the pipelines is a highly investigated topic. To eliminate the slug in an online manner real-time slug detection methods are often required. Traditionally topside pressure transmitters upstream of a 3-phase separator have been used as the controlled variable. In this paper Electrical Resistivity Tomography (ERT) has been examined as an alternative to the traditional pressure transmitters. A lab-scaled testing facility has been constructed in order to obtain test data from an ERT transmitter with 12 probes. Different flow regimes have been generated by a pump and a compressor where 2-phase flow can be tested. Based on the results, the study concludes that the ERT is able to detect the slug very well when the oil and water are well mixed. Furthermore, the traditional pressure transmitters have the limitation that pressure variations can be caused by other operating conditions than slug, such as change in the back pressure from control valves. The biggest limitation using ERT is the lack of ability to distinguish between gas and oil, and thus the ERT can only be used as an effective slug detect measurement when the oil-to-water ratio is low.
Ship-source pollution represents a threat to the environment, regardless of where it occurs. The European Union has been developing standards that aim to counter accidental, operational and intentional pollution in the waters under its member-state's jurisdiction. However, and precisely because marine pollution knows no boundaries, the EU is not coy in contemplating what ships do beyond waters under the sovereignty of its member states. This article analyzes the international legality of EU claims to port state jurisdiction over ship-source pollution. It demonstrates that port state jurisdiction is today not only a means to ensure compliance with international standards but also a means to unilaterally enforce more stringent environmental standards.
Due to the presence of long high voltage cable networks, and power transformers for the grid connection, the offshore wind power plants (OWPPs) are susceptible to harmonic distortion and resonances. The grid connection of OWPP should not cause the harmonic distortion beyond the permissible limits at the point of common coupling (PCC). The resonance conditions should be avoided in all cases.
This paper describes the harmonic analysis techniques applied on an OWPP network model. A method is proposed to estimate the harmonic current compensation from a shunt-connected active power filter to mitigate the harmonic voltage distortion at the PCC. Finally, the harmonic distortions in the compensated and the uncompensated systems are compared to demonstrate the effectiveness of the compensation.
This paper deals with two speed optimization problems for ships that sail in and out of Emission Control Areas (ECAs) with strict limits on sulfur emissions. For ships crossing in and out of ECAs, such as deep-sea vessels, one of the common options for complying with these limits is to burn heavy fuel oil (HFO) outside the ECA and switch to low-sulfur fuel such as marine gas oil (MGO) inside the ECA. As the prices of these two fuels are generally very different, so may be the speeds that the ship will sail at outside and inside the ECA. The first optimization problem examined by the paper considers an extension of the model of Ronen (1982) in which ship speeds both inside and outside the ECA are optimized. The second problem is called the ECA refraction problem, due to its conceptual similarity with the refraction problem when light travels across two different media, and also involves optimizing the point at which the ship crosses the ECA boundary. In both cases the objective of the problem is to maximize daily profit. In addition to mathematical formulations, examples and sensitivity analyses are presented for both problems.