Search Results (22)

Hydrogen is a promising environmentally friendly fuel with the potential for zero-carbon emissions, particularly in maritime applications. However, owing to its wide flammability range (4–75%), significant safety concerns persist. In confined spaces, hydrogen leaks can lead to explosions, posing a risk to both lives and assets. This study conducts a numerical analysis to investigate hydrogen flow within hydrogen storage rooms aboard ships, with the goal of developing efficient ventilation strategies. Through simulations performed using ANSYS-CFX, this research evaluates hydrogen diffusion, stratification, and ventilation performance. A vertex angle of 120° at the ceiling demonstrated superior ventilation efficiency compared to that at 177°, while air inlets positioned on side-wall floors or mid-sections proved more effective than those located near the ceiling. The most efficient ventilation occurred at a velocity of 1.82 m/s, achieving 20 air exchanges per hour. These findings provide valuable insights for the design of safer hydrogen vessel operations. Full article

To reduce weight and simplify maintenance, ship structures frequently include openings and cutouts. While these features offer practical advantages, they can weaken the structural integrity of key components. This study explores the effects of these geometric discontinuities on the double-bottom floor plates of a Panamax-class container ship under axial and transverse loads. Through numerical simulations and experimental testing, we analyzed different cutout configurations and stiffening strategies to assess their impact on stress distribution, plate thickness, and fatigue behavior. The results reveal that side cutouts significantly increase stress, particularly under transverse loads, while central openings have less impact. Additionally, increasing plate thickness consistently reduces stress levels across all models, improving structural durability. Fatigue analysis shows that certain stiffening configurations, particularly those with longitudinal stiffeners in the bottom plates, enhance fatigue life. These findings offer critical design insights for optimizing hull structures, balancing weight reduction with strength improvement. This study provides valuable recommendations for reducing stress concentrations and extending the fatigue life of ship components, contributing to more efficient and safer ship designs. Full article

The study of fire simulation and emergency evacuation in cruise ships is a challenging aspect of cruise safety research. Investigating the impact of fire byproducts on passenger evacuation is a critical issue that urgently needs to be addressed. This paper utilizes PyroSim 2022 software to establish five fire cases, analysing the fire products concentration under each case. The influence of fire products on passenger evacuation was analysed using PathFinder. The results showed that when the fire source is in the stage area, the impact of fire byproducts on passenger evacuation is relatively minor. However, when the fire source is near the exit, especially in cases 1 and 2, fire byproducts tend to accumulate in the right area of the second floor, significantly affecting passenger evacuation. Moreover, during the evacuation process, a large number of passengers exhibit herd behaviour, leading to some passengers being unable to evacuate safely. To address the congestion issue, an optimized evacuation guidance plan is proposed, that can effectively improve evacuation efficiency and reduce the average congestion time per person. This has a positive role in enhancing the safety level of cruise ship fires. Full article

Some of the barriers preventing virtual reality (VR) from being widely adopted are the cost and unfamiliarity of VR systems. Here, we propose that in many cases, the specialized controllers shipped with most VR head-mounted displays can be replaced by a regular smartphone, cutting the cost of the system, and allowing users to interact in VR using a device they are already familiar with. To achieve this, we developed SmartVR Pointer, an approach that uses smartphones to replace the specialized controllers for two essential operations in VR: selection and navigation by teleporting. In SmartVR Pointer, a camera mounted on the head-mounted display (HMD) is tilted downwards so that it points to where the user will naturally be holding their phone in front of them. SmartVR Pointer supports three selection modalities: tracker based, gaze based, and combined/hybrid. In the tracker-based SmartVR Pointer selection, we use image-based tracking to track a QR code displayed on the phone screen and then map the phone’s position to a pointer shown within the field of view of the camera in the virtual environment. In the gaze-based selection modality, the user controls the pointer using their gaze and taps on the phone for selection. The combined technique is a hybrid between gaze-based interaction in VR and tracker-based Augmented Reality. It allows the user to control a VR pointer that looks and behaves like a mouse pointer by moving their smartphone to select objects within the virtual environment, and to interact with the selected objects using the smartphone’s touch screen. The touchscreen is used for selection and dragging. The SmartVR Pointer is simple and requires no calibration and no complex hardware assembly or disassembly. We demonstrate successful interactive applications of SmartVR Pointer in a VR environment with a demo where the user navigates in the virtual environment using teleportation points on the floor and then solves a Tetris-style key-and-lock challenge. Full article

In order to reduce weight and facilitate maintenance, servicing and inspection, ship structures usually have openings and cutouts. However, these modifications frequently weaken the plates’ ability to buckle. In this work, the combined effects of geometric discontinuities (such as openings and cutouts) under diverse in-plane loads (such as horizontal compression, vertical compression, biaxial compression, and in-plane edge shear loading) are taken into consideration as the perforated plates located in the double-bottom floor of a 3000 m³ wellboat are investigated for their linear and elastic buckling behavior. In order to assess the effects of various stiffening methods and their interactions with different load scenarios, as well as fluctuating plate slenderness ratios, the research combines experimental and numerical analyses. This thorough study identifies the best stiffening technique and suggests alternative geometries that minimize structural weight through topology optimization. The research’s findings are helpful in comprehending the mechanisms underlying structural failure and in offering design and recommendation guidelines that enhance hull inspections and the assessment of structural flaws. Full article

Most facilities are structured in a repetitive manner. In this paper, we propose an algorithm and its partial implementation for a cellular guide in such facilities without GPS use. The complete system is based on iBeacons-like components, which operate on BLE technology, and their integration into a navigation application. We assume that the user’s location is determined with sufficient accuracy. Our main goal revolves around leveraging the repetitive structure of the given facility to optimize navigation in terms of storage requirements, energy efficiency in the cellular device, algorithmic complexity, and other aspects. To the best of our knowledge, there is no prior experience in addressing this specific aim. In order to provide high performance in real time, we rely on optimal saving and the use of pre-calculated and stored navigation sub-routes. Our implementation seamlessly integrates iBeacon communications, a pre-defined indoor map, diverse data structures for efficient information storage, and a user interface, all working cohesively under a single supervision. Each module can be considered, developed, and improved independently. The approach is mainly directed to places, such as passenger ships, hotels, colleges, and so on. Because of the fact that there are “replicated” parts on different floors, stored once and used for multiple routes, we reduce the amount of information that must be stored, thus helping to reduce memory usage and as a result, yielding a better running time and energy consumption. Full article

This paper presents an experimental and numerical analysis of the response of a scaled double-bottom structure with high and penetrated girders and floors impacted vertically by a rock-shaped indenter. The specimen, scaled from the bottom structure of the power-battery cabin of a new energy ship, is struck by a spherical indenter. The special double-bottom structure is designed to protect the power batteries and to facilitate heat dissipation. The experimental overall impact response, vibration acceleration, and stress of the inner bottom plate are measured in order to evaluate the impact environment in the target cabin. The investigation provides valuable information to evaluate the safety of power-battery cabins in a ship grounding scenario. The experimental results show good agreement with the finite element analyses using the explicit LS-DYNA software. The numerical analysis outlines the influence of the structural openings on the impact response and also the effect of battery mass and striking velocity on the impact environment in the target cabin. Full article

The demand for liquefied natural gas (LNG) ships is increasing for various reasons. Despite their enormous size, cargo holds inside freighters transporting LNG have traditionally been constructed by welding to high-quality standards for safety. This process traditionally relies on manual labor or semi-automatic moving devices. In this study, a methodology was designed for robot-based automated laser welding inside large LNG cargo holds. The developed approach offers a practical solution to challenging issues such as the corrugation of the membrane that forms the inner walls of LNG cargo holds and the inter-floor movement of robots. This study analyzes and restructures the work for laser welding using mobile robots inside LNG cargo holds composed of membranes. For realistic constraints, such as inter-floor movement of robots and high-quality welding of membrane corrugations, methods integrated with manual work have been proposed. Additionally, for the overall membrane laser welding of the LNG cargo hold space, an automated method using robots was suggested. The developed methodology has been realized as operational software for the movement of robots for laser welding in LNG cargo holds. Full article

The digital twinning concept stands as a remarkable opportunity to integrate sophisticated mathematical models within the context of existing manufacturing systems. Such models may provide shipyard management with predictive analytics, improving the final results at the strategic, tactical, and operational levels. Therefore, the possibility of integrating the Markovian-framework-based finite-state method into the context of ship production is presented in this study, including its outline, digital thread, and factory-floor data reliance. First, the predictive analytics problem is addressed by the finite-state method in the case of the shipyard’s fabrication line, and the obtained results are validated afterward using a numerical model through discrete-event theory. The predictive analytics indicate an almost ideal balancing of the fabrication line, except for the buffers storing stiffeners before the coat-dying and marking operations. In addition, the improvability analysis of the shipyard’s fabrication lines extended the scope of the predictive analytics using bottleneck identification and affecting the key performance indicators through a digital thread, as well as by improved maintenance strategies. Full article

Wood is one of the most abundant biomaterials on Earth, which has been used for centuries in construction applications including furniture, roofing, flooring, and cabinetry. However, wood chips—which are a low-quality and plentiful waste byproduct of lumber milling, woodworking, and shipping operations—have low economic value and complicated disposal methods. In this paper, we propose a strategy for wood chip reuse through the fabrication of bio-based building insulation foam. Through a high-temperature chemical treatment delignification process, we introduced additional small pores within the wood chips, effectively lowering their thermal conductivity, and used them in combination with a binding agent to produce a porous insulation foam. The porous insulation foam achieved a low thermal conductivity of 0.038 W/(m·K) and a high compressive strength of 1.1 MPa (70% strain). These characteristics demonstrate that wood waste can be repurposed into an effective building material, addressing challenges in both waste management and sustainable construction. Full article

Indoor path loss models characterize the attenuation of signals between a transmitting and receiving antenna for a certain frequency and type of environment. Their use ranges from network coverage planning to joint communication and sensing applications such as localization and crowd counting. The need for this proposed geodesic path model comes forth from attempts at path loss-based localization on ships, for which the traditional models do not yield satisfactory path loss predictions. In this work, we present a novel pathfinding-based path loss model, requiring only a simple binary floor map and transmitter locations as input. The approximated propagation path is determined using geodesics, which are constrained shortest distances within path-connected spaces. However, finding geodesic paths from one distinct path-connected space to another is done through a systematic process of choosing space connector points and concatenating parts of the geodesic path. We developed an accompanying tool and present its algorithm which automatically extracts model parameters such as the number of wall crossings on the direct path as well as on the geodesic path, path distance, and direction changes on the corners along the propagation path. Moreover, we validate our model against path loss measurements conducted in two distinct indoor environments using DASH-7 sensor networks operating at 868 MHz. The results are then compared to traditional floor-map-based models. Mean absolute errors as low as 4.79 dB and a standard deviation of the model error of 3.63 dB is achieved in a ship environment, almost half the values of the next best traditional model. Improvements in an office environment are more modest with a mean absolute error of 6.16 dB and a standard deviation of 4.55 dB. Full article

This article describes the results of the retrospective numerical simulation of wind waves in the Sea of Azov using the SWAN spectral wave model and the ERA-Interim global reanalysis for 1979–2019. A digital model of the sea-floor relief of the Sea of Azov was used for the calculations. This model was built using a bathymetric map of the Sea of Azov, as well as nautical charts and remote sensing data. Verification of the model for the conditions that characterize the Sea of Azov was conducted using data from ship observations of wind waves. The features of the mean long-term wind wave patterns, as well as the seasonal, interannual, and interdecadal dynamics were presented. The main focus was on the following parameters: significant wave height, wave period, and wave direction. A description of storm conditions and a comparison with surge phenomena and ice conditions was also completed. The results indicated that, in contrast to Taganrog Bay, the wave patterns were heavily influenced according to the time of year (i.e., the seasons). The maximum wave heights were typical for the cold season of the year but not for the ice-free period. The interannual dynamics of wind waves were characterized by the alternation of three five-year periods of strengthening and weakening of wind waves. After 2002, the wave height increased in the summer and autumn seasons and slightly decreased in winter and spring. A shift of the storm season to a warmer period was also detected. Full article

Nowadays, the application of composite materials and light-weight structures is required in those industrial applications where the primary design aims are weight saving, high stiffness, corrosion resistance and vibration damping. The first goal of the study was to construct a new light-weight structure that utilizes the advantageous characteristics of Carbon Fiber Reinforced Plastic (CFRP) and Aluminum (Al) materials; furthermore, the properties of sandwich structures and cellular plates. Thus, the newly constructed structure has CFRP face sheets and Al stiffeners, which was manufactured in order to take experimental measurements. The second aim of the research was the elaboration of calculation methods for the middle deflection of the investigated sandwich-like structure and the stresses that occurred in the structural elements. The calculation methods were elaborated; furthermore, validated by experimental measurements and Finite Element analysis. The third main goal was the elaboration of a mass and cost optimization method for the investigated structure applying the Flexible Tolerance optimization method. During the optimization, seven design constraints were considered: total deflection; buckling of face sheets; web buckling in stiffeners; stress in face sheets; stress in stiffeners; eigenfrequency of the structure and constraints for the design variables. The main added values of the research are the elaboration of the calculation methods relating to the middle deflection and the occurred stresses; furthermore, elaboration of the optimization method. The primary aim of the optimization was the construction of the most light-weighted structure because the new light-weight sandwich-like structure can be utilized in many industrial applications, e.g., elements of vehicles (ship floors, airplane base-plate); transport containers; building constructions (building floors, bridge decks). Full article

This article is an attempt to analyse the master frame form characterised by a flat floor-timber, a sharp or shaped turn of the bilge, and more or less straight sides. This form of master frame is associated with the Mediterranean architecture of the ‘frame-based’ principle, as attested from the end of the 5th century to the beginning of the 6th century AD Dor 2001/1 shipwreck (Israel), which is considered as one of the five origins (Root 4: Nilotic-riverine) of the ‘frame-based’ architecture. A series of medieval and modern wrecks of coastal ships and galleys bear witness to this form of master frame linked more generally to the Mediterranean whole moulding. In view of the consistency of these archaeological as well as ethnographic evidence on traditional Mediterranean shipbuilding, this form of master frame with a flat floor-timber appears to be one of the most revealing ‘architectural signatures’ of the practices of Mediterranean shipyards. Full article

The paper presents results of tests related to smoke optical density conducted on four various textile floor coverings for the needs of building interior design. Smoke emission is one of basic elements that characterize the fire environment. Consequently, the objective of the paper was to carry out a comparative analysis of smoke generation of chosen floor coverings for selected thermal exposures and in the presence or absence of a stimulus igniting the volatile gaseous phase (pilot flame). For the needs of our experimental research use was made of polypropylene, polyester, composite of wool, cotton, viscose and polyamide floor coverings. The highest value of the maximum specific optical density of smoke (494.7) was recorded for the floor covering consisting of 100% polypropylene (with higher fiber) under flameless combustion conditions (without the pilot flame). The polypropylene floor covering without underlay proved to be the best material from among all the tested ones with respect to smoke generating properties, and its samples offered the lowest value of optical density after 4 min for testing variants without the application of a pilot burner, with the flammable phase of decomposition products of this sample during the testing in which the burner was used to ignite at the latest. Experimental research has been carried out based on the standard ISO 5659–2:2017–08. The tests results were compared with international optical smoke density requirements for the interior design of ships and trains. Full article