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  • Wójcik, Łukasz; Bulzak, Tomasz; Winiarski, Grzegorz; Szala, Mirosław (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    This article presents the results of computer simulations used to investigate the forming of a hollow coldworked forging with an outer flange. Numerical simulations were performed in Deform 2D/3D using a calculation module for axial-symmetric cases. A ϕ57×12.5 mm tube-shaped billet from 42CrMo4 grade steel was used. The forming process involved two and three stages, consisting of extrusion the shaft portion and forging the flange. The objective of this research was to determine the accuracy of the forming process used to produce the hollow part. This technology was analyzed using the effective strain distributions, the Cockcroft-Latham fracture criterion values, and the forming force progression. The results showed that it was possible to use this three-stage process to forge elements from a tube-shaped billet.
  • Szelangiewicz, Tadeusz; Żelazny, Katarzyna (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    In this paper, an experimental model has been developed to study an unmanned ship. Two aft azimuthal propellers and two bow tunnel thrusters were used to propel the ship. In order to develop algorithms and a computer program to control the model, it is necessary to determine the hydrodynamic characteristics of the propellers installed in the model. The propellers are very small; therefore it is impossible to use approximate methods of calculating the thrust of the ship’s propellers. The characteristics of the thrust of the propellers installed in the model were measured experimentally. This paper has given a description of the test stand and the results of the measurement of the thrust forces of the propellers installed in the model of an unmanned ship.
  • Sakaki, Abdollah; Kerdabadi, Mohsen Sadeghian (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    Computational fluid dynamics (CFD) has progressed rapidly in the past fifty years and is now used in many industrial fields, such as air, space, and marine engineering. CFD has an irreplaceable role in marine design and scientific research, and its applications within this field continue to grow with the development of computers. CFD is used to quickly and inexpensively simulate fluid behaviour using the Reynolds Averaged Navier–Stokes (RANS) equations to calculate hydrodynamic coefficients, which are needed in manoeuvrability studies of underwater vehicles (UWV). Here, these computations are performed for six geometrical shapes that represent typical autonomous underwater vehicles (AUVs) currently in use. Resistance test simulations at up to 20o drift angles were conducted for AUVs with different length-to-diameter ratios. The results were compared with the experimental data and current quasi-experimental relationships, which suggested that the CFD predictions were adequately precise and accurate. These predictions indicated that there was a non-linear relationship between forces and moments and the lateral speed. Moreover, both linear and non-linear hydrodynamic coefficients were calculated.
  • Nazemian, Amin; Ghadimi, Parviz (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    This paper investigates improving the leading-edge of a hydrofoil with sinusoidal protuberances based on its hydrodynamic performance. The original hydrofoil geometry was inspired by the leading edge of the flipper of a humpback whale. A multi-step optimization process was performed for a 634-021 hydrofoil. The free-form deformation technique defined the shape parameters as a variable design, and these parameters included the amplitude of the leading-edge protuberances, which ranged from 0 to 20% of the chord length, and the corrugate span, with 3 and 4 crests. The flow characteristics of a parametric hydrofoil were examined using a CFD solver, and the lift, drag, and lift-to-drag ratio (L/D) were computed as responses to the optimization cycle. To accomplish this, two design study methods were sequentially applied at different angles of attack. A full factorial design sweep tool was applied that went through all parameter value combinations, and an RBF-based surrogate model was constructed to investigate the system behavior. The results indicated the existence of an optimum design point, and the highest L/D ratio was determined to be 10.726 at a 12° angle of attack.
  • Motallebi, Mohammad; Ghafari, Hamidreza; Ghassemi, Hassan; Shokouhian, Mehdi (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    In this paper, the second-order hydrodynamic force on fixed and floating tandem cylinders has been calculated and different parameters have been taken into consideration. An incident wave is diffracted by the fixed cylinder, and as a result low-frequency waves radiate toward the floating cylinder and cause low-frequency second-order hydrodynamic forces to act on the surface of the floating cylinder. The interactions between the fixed and floating cylinders have been investigated by changing the distance between them, as well as the draft and radius of the floating cylinder. By employing perturbation series analysis over the wetted surface, the second-order wave excitation force has been calculated. The maximum force applied on the floating cylinder becomes non-dimensional when considering it with and without the fixed cylinder. The results showed the effect that the existence of the fixed cylinder had on the increase in the second-order forces is quite evident where, for a significant parameter of the floating cylinder, the force in the heave direction was enhanced by up to 1.55 times.
  • Krystosik-Gromadzińska, Agata (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    The human factor is one of the main reasons for fires in engine rooms and most of the scenarios are very similar. Fires in engine rooms are usually associated with fuel or oil leaking onto a hot surface. Furthermore, engine rooms are very inhospitable places to work. Noise, vibration and high temperatures are most frequently mentioned by crews as negative factors that influence their work. The adoption of a safety culture is one of the ways to increase the fire safety level in engine rooms. Understanding and accepting the necessity of building a safety culture among engine room crews can effectively influence their standard of work. Safety management procedures are an important part of building a safety culture. The change in labor standards must be built on a safety culture among crews.
  • Dounar, Stanislau; Iakimovitch, Alexandre; Jakubowski, Andrzej (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    In this paper, Finite Element Method (FEA) harmonic analysis of the changes caused by raising the centerline of a large, precise lathe is presented. Two standalone dynamic subsystems (“Rotor Shaft” and “Support”) are revealed and the resilience of the “Rotor Shaft” to the raising procedure is stated. The three subsystems of the “Support” class are much more dynamically pliable, only the main eigenmodes of the shaft and supports are excited in the 0…100 Hz range (MR1“Half-wave” and MS1…3 “Radial pecking”). Mounting the lunette suppresses the MR1 peak by a factor of two; therefore the lunette is strongly recommended, with an optional tuned-mass damper (TMD). The support’s resonant frequencies MS1…3 are more deleterious for precision; they should be omitted or weakened using TMD’s that are attached to the supports. For the above conditions, raising the centerline (up to 600 mm) may be included in the lathe renovation program.
  • Winiarski, Jacek; Szóstakowski, Marcin (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    How is the implementation of public transport services perceived by the public in the context of the sharing economy? What social and economic elements determine their development? The task of this article is to look for answers to questions formulated in this way. A quantitative method was used to conduct the research; the technique that was used was the CASI online survey. Profitability calculations were carried out and compared for three variants of vehicle use: rented, new and used. The deadlines for exceeding the profitability thresholds were set under the assumed preconditions for the analyzed variants. The results that were obtained provided an assessment of the customers’ opinions on the use of elements of the sharing economy in public passenger transport, and enabled the formulation of determinants of the popularization of these solutions as well as a determination of the cost-effectiveness thresholds for practical applications.
  • Özkan, Emin Deniz; Koçer, Umay Uzunoğlu; Nas, Selçuk (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    The proper selection of statistical distributions is important for modeling port operations using simulations or queuing theory. The aim of this study was to determine the appropriate statistical distributions for modeling random processes related to ship operations in ports, including ship arrivals, berthing maneuver processes, service processes, and unberthing maneuver processes. A literature review was performed on the statistical distributions used in these random processes. In addition, the port data on ship operations gathered from three different ports in Turkey were examined. Goodness of fit tests were conducted to determine the appropriate distribution for each process.
  • Sakharov, Vladimir V.; Chertkov, Alexandr A.; Ariefjew, Igor B. (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    Task planning involves automating the creation of the routes for vessels with known coordinates in a confined space. The management of vessel release in a given area affects the time required for a vessel to complete its voyage, and maximizing vessel performance involves identifying the shortest route. A key issue in automating the generation of the optimal (shortest) routes is selecting the appropriate mathematical apparatus. This paper considers an optimization method based on a recursive algorithm using Bellman-Ford routing tasks for large dimensions. Unlike other optimization techniques, the proposed method enables the shortest path to be assessed in a network model with a complex topology, even if there are arcs with negative weights. The practical implementation of the modified Floyd algorithm was demonstrated using a sample automated build and using it to calculate a network model with a complex topology, using an iterative procedure for a program prepared in MATLAB. Implementation of the computer model is simple, and unlike existing models, it eliminates restrictions associated with the presence of negative weights and cycles on a network and automates search shortcuts in ground branch functional means in MATLAB. To confirm the accuracy of the obtained results, we performed an example calculation using the network. The proposed algorithm and recursive procedure are recommended for finding energy-efficient solutions during the management of mobile objects on waterways.
  • Bąk, Andrzej (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    In this article, a systematic solution for mitigating the DFG (Derelict Fishing Gear) problem has been presented using an example of a DFG wreck operation. The planning process has been described in detail and the influence of ghost net recovery on the marine environment has been shown. The research was performed on selected wrecks found in the Polish economic zone and the method consisted of scanning the sea bottom using 2D sonar. Based on the information obtained by the sonar, the ghost nets were later retrieved using a creeper (in cases where the ghost nets were lying on the sea bottom) or with the help of divers (in cases where the nets were sitting on the wrecks). The results have shown that, taking into consideration the research area of the Baltic Sea, the presented method will be satisfactory in most cases.
  • Wieczorek, Agnieszka (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    Gas carriers are one of the most advanced types of ships and are equipped with the latest technological achievements. Due to the development of this industry, the demand for ethylene transport by sea has increased significantly in recent years. Nonetheless, it is one of the most problematic loads in terms of loading operations. Due to the small density differences between ethylene and nitrogen, ethylene is one of the most problematic hydrocarbons with respect to the efficient gasification of cargo tanks. Additionally, ethylene is one of the most expensive cargoes carried on gas carriers. The above aspects make it necessary to carry out a detailed analysis of the flushing of nitrogen-loaded cargo tanks with ethylene vapors to determine the range of technical parameters to enable more efficient tank gassing-up. This paper provides a detailed analysis of an experimental cargo tank gassing-up operation on an ethylene carrier. The process was carried out in accordance with previously-determined assumptions to optimize the discussed operations, assess how the cargo tank pressure influences this process, reduce cargo loss during gassing-up, and eliminate cargo loss during its cooling. The conclusions from this experiment provide guidelines for subsequent tests.
  • Szaruga, Elżbieta (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    This paper presents an approach to rationalize the energy consumption of road transport towards sustainability in a steady-state economy. The research hypothesis is that the rationalization of the energy consumption of road transport is affected by drift and shocks, which desynchronizes the adjustment mechanism from equilibrium. The objective of this research was to incorporate the model of energy consumption of road freight transport with the goals of sustainability by considering ecological and constructivist rational orders, the issue of order drift, and the occurrence of shocks. The research investigated Poland from the first quarter of 2004 to the fourth quarter of 2018. A model for rationalizing the energy consumption of road transport was constructed using the vector error correction model and cointegration techniques. The model revealed one cointegrating relationship and showed statistically significant unlimited drift. The level of changes to long-term equilibrium appeared respectively for GDP – 1.8%, PPI for energy – 7.3%, and for energy consumption – 10.9%. We observed a weak sustainability between the energy consumption of road transport and GDP and a strong sustainability between energy consumption of road transport and PPI energy. It was determined that price shocks had a positive impact (at the estimated point level around 0.06) and supply and demand shocks had a negative impact (at the level estimated point around –3).
  • Specht, Mariusz; Szmagliński, Jacek; Specht, Cezary; Koc, Władysław; Wilk, Andrzej; Czaplewski, Krzysztof; Karwowski, Krzysztof; Dąbrowski, Paweł S.; Chrostowski, Piotr; Grulkowski, Sławomir (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    Each year, global navigation satellite systems (GNSS) improve their accuracy, availability, continuity, integrity, and reliability. Due to these continual improvements, the systems are increasingly used in various modes of transport, including rail transport, the subject of this publication. GNSS are used for rail passenger information, rail traffic management, and rail traffic control. These applications differ in the positioning requirements that satellite navigation systems must meet. This article presents the methods and systems of rolling stock location and tracking using the Polish State Railways (PKP) as an example. The information on the equipment used for train positioning is not specified anywhere, hence they may differ, even for the same multiple units travelling in different parts of the country. In addition, the publication presents the progress of the European Train Control System (ETCS) implementation by the PKP.
  • Skoko, Ivica; Lušić, Zvonimir; Pušić, Danijel (Scientific Journals Maritime University of Szczecin, Zeszyty Naukowe Akademia Morska w Szczecinie, )
    The offshore oil & gas industry is one of the most important industries in the world and has a direct impact, either positive or negative, on the global economy. In order to ensure continuous exploration and production, various offshore installations must be supplied with all the necessary materials and cargo on a regular daily basis. The most convenient way to do this is by using different types of offshore supply vessels, which constitute one of the most expensive factors in the logistics supply chain in the offshore oil and gas industry. Reliable, cost-efficient, environmentally friendly transport and technically “fit for purpose” offshore vessels are the goal of any oil & gas company. This article presents a review of the offshore oil & gas market and the business strategy which includes offshore supply vessels. The research includes SWOT analyses to emphasize the advantages and challenges in the oil & gas industry and presents the correlation between the crude oil price and the daily rate of offshore vessels and aims to predict future movements in the market.

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