Scientific Journal of Maritime Research - Pomorstvo

Numerical Study of the Effect of Depth Immersion and Rotation Direction on the Performance Cross-Flow Savonius Turbine

Tue, 22 Oct 2024 00:00:00 +0200

Energy supply is a critical variable affecting modern life. Indonesia has many renewable energies sources and one of them is ocean current. Savonius turbines, which are effective in low-speed currents, have been widely studied in their vertical form, but there has been little progress on cross-flow Savonius turbines. The turbine performance is investigated in this study by observing the behaviour caused by the influence of depth immersion, given that the surface of the submersible medium and the surface based can influence the turbulence caused. Therefore, the cross-flow Savonius turbine will be placed in three different depth conditions: 0.33H; 0.5H and 0.66H. Analysis is done with Computational Fluid Dynamics (CFD) software. The turbine's rotation direction is also set in two conditions (clockwise and counterclockwise). All these scenarios result that turbine with 0.66H and clockwise condition gives the highest results with Cp value at 0.249. The vortices flow pattern created by the clockwise configuration tends downward, in contrast to the counterclockwise which points upward. The cross-flow Savonius turbine works optimally in low TSR where its performance is greatly affected by torque.

EFFICIENT MANAGEMENT OF IMPORT CONTAINERS ALLOCATION IN A CONSTRAINED ENVIRONMENT

Hizia Amani, Linda Bouyaya, Rachid Chaib, Mohamed seghir Amani — Tue, 22 Oct 2024 00:00:00 +0200

Ports play an essential role in international trade, and any inefficiency can lead to costly delays and major disruptions. Therefore, the efficiency of port operations is crucial for the smoothness of global supply chains helping reduce the risk of congestion and accidents, thereby enhancing maritime safety. Optimizing container management is particularly significant in this context. Thus, the problem of storage space allocation problem is a critical aspect of managing port operations, significantly influencing the efficiency of the retrieval process and the number of reshuffles. This study proposes a new policy, aimed at optimizing the use of space for import containers in a constrained environment. This policy incorporates considerations to facilitate the retrieval process and reduce the expected number of reshuffles. As a case study, we have taken the Port of Annaba in Algeria. Using an improved genetic algorithm and a heuristic approach, we achieved up to 22% improvement compared to the existing port policy. This demonstrates the effectiveness of our policy in enhancing port operations within spatial constraints.

Coastal Zone and Maritime Common Good Participatory Allocation

Borna Debelić — Tue, 22 Oct 2024 00:00:00 +0200

The paper presents results of the research focused on analysing applicable allocation approaches (general mechanisms) regarding coastal zones and maritime common good. We identified relevant general stakeholder groups and two general allocation approaches, one with decision-making authority granted exclusive to public authorities, and other – participatory approach – based on self-governing and deliberative inclusion and proactive participation of all relevant stakeholders in the allocation decision-making process and governing mechanism. The research also utilises application of agency theory to maritime common good and coastal zone allocation, evaluating identified allocation approaches in the light of the agency theory. The research also encompasses an in-depth literature analysis, complementary accompanying previous research in the field and evaluating compatibility of participatory allocation approach with modern institutional framework addressing coastal zone management in the Mediterranean. The importance of further developments of maritime common good and coastal zone allocation approaches and mechanisms, based on active participation and partnership of stakeholders in the decision-making process, is emphasized in order to further strengthen the potential for stronger and fruitful utilisation of information background (local knowledge) from local population necessary to sustainably improve complex allocation process of maritime common good on the long run.

Zero-Shot Learning in Maritime Domain: Classification of Marine Objects using CLIP

Ivan Lorencin, Domagoj Frank, Damir Vusić — Tue, 22 Oct 2024 00:00:00 +0200

Maritime security and monitoring are essential for global trade, environmental protection,
and national defense. Traditional machine learning models have been effective in recognizing and
classifying maritime objects, but their reliance on large, labeled datasets poses challenges,
particularly in dynamic environments where new and unforeseen objects frequently emerge. This
study explores the application of Zero-Shot Learning (ZSL) to the maritime domain, leveraging the
CLIP model to classify maritime objects with minimal labeled data. A custom dataset comprising
1,438 images was used to evaluate the performance of various CLIP model variants. Our findings
indicate that CLIP models, particularly the "clip-vit-large-patch14-336" variant, achieve high
classification accuracy, with AUC values approaching 1.0 across most classes. However, challenges
remain in handling rare or ambiguous classes such as cargo ships, where F2 scores suggest
variability in recall and precision. Additionally, the study highlights the potential limitations of
these models, including their dependency on dataset diversity and the risk of overfitting to specific
data characteristics. The "clip-vit-large-patch14-336" model is identified as the most balanced and
reliable option, offering a strong foundation for enhancing maritime situational awareness and
supporting diverse maritime applications.

Seawater exposure effect on crashworthiness of CFRP tubes

Tino Načinović, Goran Vukelić, Benjamin Mihaljec, Ljubomir Pozder — Tue, 22 Oct 2024 00:00:00 +0200

This study investigates the effects of seawater exposure on the crashworthiness of two types of carbon/epoxy composite tubes under quasi-static compression. Carbon/epoxy composites, widely used in maritime structures due to their high strength-to-weight ratio and corrosion resistance, may experience altered mechanical properties when exposed to harsh marine conditions. To evaluate these effects, quasi-static crushing tests were conducted on composite tubes after a one-month exposure to natural seawater. Composite tubes were manufactured using hand layup and prepreg technique. By analyzing the behavior of these composite structures under controlled compression, the study aims to provide insights into their structural integrity in marine environments. Results indicate a significant impact of seawater exposure on the crashworthiness of carbon/epoxy composites. The maximum tensile force is considerably lower after the exposure, and hand layup specimens generally withstand the exposure much better than prepregs. The findings contribute to a deeper understanding of material behavior in marine applications, offering practical guidelines for designing and maintaining composite-based maritime infrastructure.

Evaluation of Occupational Health and Safety Management System Performance in Shipyard Businesses with FAHP and FPROMETHEE Methods

murat yorulmaz, Mehmet Arif ÖZTÜRK — Tue, 22 Oct 2024 00:00:00 +0200

Shipyards are places where new ships are built, routine and mandatory maintenance and dismantling of ships are carried out and a wide range of work equipment and chemicals are used during these processes. The fact that most of the world is covered with water and that maritime transportation is advantageous compared to other types of transportation brings maritime transportation to the forefront. This situation also leads to an increase in work intensity in shipyards. Therefore, occupational health and safety (OHS) practices are also important in shipyards. In this context, this study aims to evaluate the OHS Management System (OHSMS) performances of shipyard enterprises and to rank the shipyard enterprises selected as alternatives according to their OHSMS performances in line with the determined criteria. In the first stage, five main and 16 sub-criteria as OHSMS performance criteria and five alternative shipyard enterprises were identified through literature research. In line with the expert opinions, the weights of the criteria were found with the Fuzzy Analytic Hierarchy Process (FAHP) method, one of the multi-criteria decision-making methods, and the alternative priority order for the criteria was determined with the Fuzzy PROMETHEE (FPROMETHEE) method using the results obtained from the FAHP method. As a result of the analysis, the main criterion "Management Review" was determined as the criterion with the highest weight ratio. As a result of the operations carried out with the criterion weights determined by FAHP, Shipyard 3 alternative was ranked first in terms of OHSMS performance in the priority ranking made by using FPROMETHEE method. In this study, OHSMS performance evaluation in shipyard enterprises has been carried out by using FAHP and FPROMETHEE methods, which are multi-criteria decision-making methods, and the findings have contributed to the shipyard sector and the literature.

Comparative analysis of chartering in nautical tourism in the Republic of Croatia and competitive countries of the European Union

Ivona Brnić — Tue, 22 Oct 2024 00:00:00 +0200

Nautical tourism is an economic phenomenon that has played an increasingly important role in the economic growth of the coastal states of the European Union in recent decades. Strictly speaking, nautical tourism is a part of tourism that, according to data from 2021, accounts for as much as 15.9% of the total GDP of the Republic of Croatia. Despite these high numbers, Croatia lags behind European countries such as France, Spain and Italy due to its relatively weak nautical tourism offer. Considering the climatic and spatial conditions and the long coastline rich in relief, Croatia still has a lot of unused potential for the development of nautical tourism. Nautical charter is one of the most underdeveloped activities of nautical tourism, especially in the area of luxury charter, which refers to the rental of luxury yachts. Daily and multi-day charters are more common in Croatia, but the lack of differentiation of the fleet and inadequately trained personnel make it impossible for the services offered to meet the demand. This is particularly evident in the period following the Covid 19 pandemic, which has greatly changed the economic and social point of view of boat users.

The aim of this scientific article is to compare the nautical tourism of the Republic of Croatia and selected countries of the European Union, with special attention to the nautical charter, in order to gain insight into the current state of the market and identify advantages and disadvantages. of charter tourism to enable the further development of the Republic of Croatia in the above-mentioned field. Through the collected statistical data the prices and quality of the nautical charter service in Croatia and competing countries of the European Union, the results were compared and analyzed. Considering the affordability of renting motor and sailing yachts, the competitiveness of the Republic of Croatia on the European market is undeniable. However, this work also examines whether the existing infrastructure and superstructure can support the potential development of nautical charter in the Republic of Croatia.