The key to the realization of air-water trans-medium flight lies in the profile design of trans-medium flight and the satisfaction of different requirements of aerodynamic efficiency for air cruise and airfoil for underwater glide. In this paper, a trans-medium flight profile scheme based on the fusion design of traditional fixed-wing vehicles and underwater gliders was proposed with a small trans-medium vehicle as the platform. Several typical working conditions were determined, and alternative airfoils based on NACA00 and NACA44 series were selected according to the working conditions. The compressible flow model of Fluent was used to carry out numerical analysis on the alternative airfoil set. The aerodynamic and hydrodynamic characteristics of the alternative airfoils in air and water, such as lift-to-drag ratios, lift line slope, lift and drag coefficients, and torque coefficients were calculated by numerical simulation, which were then used as the optimal objective function and constraint conditions of the airfoil of the trans-medium fixed-wing vehicle. The relationship between the preferred airfoil under the underwater navigation profile and the corresponding flight/underwater motion parameters was emphatically analyzed, especially the influence of the change in airfoil camber on the underwater endurance time and range, so as to provide the airfoil optimization decision for the scheme design of the trans-medium vehicle, and the established analysis process can provide a reference for the parameter optimization of the airfoil.
Nonlinear soil–pile–structure interaction (SPSI) phenomena are known to play a vital role in the response of bottom-fixed marine structures. For such structures, these phenomena are commonly considered by the imposition of p-y, τ-z, and q-z springs, representing the lateral and axial shaft and axial base soil resistances, respectively. The importance of each resistance mechanism depends on the type of foundation system, with only very limited studies investigating their roles in the response of piled marine structures, such as jetties. Within this context, this study presents numerical three-dimensional pushover analysis results for two marine jetties, a smaller model with four piles and a larger model supported by twenty-four piles. SPSI effects are considered through p-y, τ-z, and q-z springs, the behaviours of which are determined by following commonly employed procedures. The structures’ responses are investigated under the influence of various assumptions regarding the behaviours of springs, as well as steel plasticity. The current investigation underscores the substantial influence of the axial soil–pile interaction on the response of the jetty, particularly in terms of its failure mode. Moreover, it demonstrates the importance of incorporating p-y springs, even though the choice between their linear or nonlinear constitutive behaviour is found to be less critical. Finally, the study concludes that the behaviours of the springs significantly affect the system’s ductility and the degree of steel yielding in the piles, while also highlighting the unconservative influence of neglecting SPSI phenomena.
With the widespread application of array signal processing, the estimation of direction of arrival(DOA) as the core problem of array signal processing has made significant progress. This paper first summarizes the traditional algorithms based on beamforming for narrowband target direction estimation relying on uniform linear arrays and emerging algorithms in the past decade. Then, it analyzes the reasons for the limited resolution of traditional beamforming-based methods and discusses higher-resolution methods such as adaptive beamforming direction spectrum, subspace methods, and compressed sensing. Furthermore, for the needs of practical applications, the paper summarizes the progress of broadband target DOA estimation methods, sparse array-based DOA estimation methods, and two-dimensional DOA estimation methods. Finally, the new advances of artificial intelligence-based methods in DOA estimation are introduced. The research in this paper can be applied to modern radar/sonar detection, radio communication, and navigation, showing high application value.
Chih-Wen Cheng, Yu-An Tzeng, Ming-Hsiung Chang
et al.
This study presents an optimized system for ship route planning. Computational fluid dynamics simulations were used to modify Kwon’s semi-empirical speed loss estimation method, enabling efficient route planning under variable sea conditions. The study focused on improving the prediction of speed loss in irregular waves for container ships and further applying this to ship-optimized voyage planning. Dynamic programming was used for optimized voyage planning by modifying the ship course in response to meteorological data; this approach could balance both energy efficiency and safety. The modified speed loss predictions aligned closely with the simulation results, enhancing the reliability of weather routing decisions. Case studies for trans-Pacific and trans-Atlantic voyages demonstrated that the proposed system could significantly reduce the voyage time. These findings highlight the potential of real-time updates in voyage planning. The proposed system is a valuable tool for captains and fleet managers. The applicability of this system can be further broadened by validating it on different ship types.
The paper discusses the role of social marketing in preventing health-related harmful habits such as tobacco consumption and smoking. These habits are the causes of deadly diseases such as lung cancer, tuberculosis, and other chronic infections which are detrimental to life of the people. Children fall prey to the wrong habits in the wrong company and become tobacco addicts. So many cases of teen drug addicts are reported in a large number. They have a lack of conscience at a tender age and negligence of their counselling and awareness increases the number of smokers, drunkards, and drug addicts. Once they are afflicted with the diseases they must run for medicines and treatment. Therefore, it should be prevented before suffering as the saying goes, “Prevention is better than cure “. They are unaware that they are prevented not only by clinical treatment and medicines but also by social awareness and education. Social mobilization of the people through awareness programs, education, camps, campaigns, etc. is known as social marketing. The significance of social marketing is its effects on the prevention of physically detrimental habits in the youth which contributed a lot to the reduction of cases of diseases. The role of government programs, educational and medical institutions, social workers, and NGOs is worth applauding in India which undertake and complete projects, organize awareness camps, and educate parents and youths to save themselves from the consumption of harmful substances. It has also produced good output in India that the cases of smoking and drug addiction have reduced to support the country’s development as India is advancing towards becoming the third largest economy and a developed country by 2030 and 2047 respectively.
There are ever-increasing efforts on utilising non-conventional energy resources so as to reduce the global carbon footprint and reduce pollution caused by extensive use of energy from conventional sources. At the same time, the energy extraction from the abundant marine renewable energy resources available offshore need more development due to difference in the levelized cost of energy (LCOE) compared to energy extracted onshore, though the difference in the cost of energy is getting reduced faster than expected. Meanwhile hundreds of offshore platforms already existing in oil and gas industry will undergo decommissioning at the end of its life; which will require the platform to be removed or reused. In this context, the reuse possibility of such decommissioned offshore platforms to be used as support structures for marine renewable energy applications is examined. This paper presents a review on the research efforts on this topic and a discussion on the various aspects involved in the possible reuse of decommissioned offshore fixed platforms for marine renewable energy applications. Journal of Naval Architecture and Marine Engineering Vol 19(2), December, 2022 p. 71-82
Maritime transportation is one of the major contributors to the development of the global economy. To ensure its safety and reduce the occurrence of a maritime accident, intelligent maritime monitoring and ship behavior identification have been drawing much attention from industry and academia, among which, the accurate prediction of ship trajectory is one of the key questions. This paper proposed a trajectory prediction model integrating the Convolutional LSTM (ConvLSTM) and Sequence to Sequence (Seq2Seq) models to facilitate simultaneous extraction of temporal and spatial features of ship trajectories, thereby enhancing the accuracy of prediction. Firstly, the trajectories are preprocessed using kinematic-based anomaly removal and Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) to improve the data quality for the training process of trajectory prediction. Secondly, the ConvLSTM-based Seq2seq model is designed to extract temporal and spatial features of the ship trajectory and improve the performance of long-time prediction. Finally, by using real AIS data, the proposed model is compared with the Seq2Seq and Bidirectional LSTM based on attention mechanism (Bi-Attention-LSTM) models to verify its effectiveness. The experimental results demonstrate that the proposed model achieves excellent performance in predicting turning trajectories, good predictive accuracy on straight line motions, and greater improvement in prediction accuracy compared to the other two benchmark models. Overall, the proposed model represents a promising contribution to improving ship trajectory prediction accuracy and may enhance the safety and quality of ship navigation in complex and volatile marine environments.
During the process of container ship transportation, the berthing time cost of the ship in port is extremely important. Container allocation and quay crane (QC) operation greatly affect the berthing time. Currently, few scholars have combined import/export container allocation and QC operation, making it urgent to study ship stowage and QC collaboratively. In this paper, a mixed-integer programming model is established for the ship multi-port master bay plan problem (MP-MBPP), based on the operation of twin 40-foot QCs. The aim of this model is to minimize container rehandling and the time required for twin 40-foot QCs operation movement. A variety of new stowing strategies have been designed, and the improved coded particle swarm optimization algorithm (PSO) is used to optimize the position of double-bays, reducing the number and distance of QC movements and minimizing ship berthing time. By comparing the impact of different stowage rules on ship berthing time through examples, verification shows that the proposed stowage model and solving algorithm can obtain optimized solutions. Under the same initial conditions, the double-bay stowage based on the twin 40-foot QCs can improve operation efficiency by at least 20.3%, compared to the single-bay with ordinary QC, verifying the effectiveness of the proposed method.
The control centers of wind power plants are usually located in coastal tidal flat areas. A thick fill should be placed at the original ground level to ensure that the design elevation of the control centers is maintained above the water table. However, the filling would cause a long-term ground settlement and further lead to the development of the negative skin friction (NSF) of the pile foundations for the control centers. The CPTU tests were conducted to calibrate the soil properties, of which the rationalities were verified by comparisons of the pile-bearing capacities between the full-scale axial compressive tests and β-method. The numerical analysis method was then established to investigate the influence of additional ground pressures on the pile axial bearing behavior over time and the influence of NSF caused by consolidation on pile-bearing capacity. Finally, a simple procedure was further employed to investigate the evolution of the long-term pile-bearing behavior.
In crowded waters, the incidence of collision accidents of multiple vessels has increased significantly, most of which can be ascribed to human factors, particularly, human decision-making failures and inobservance with International Regulations for Preventing Collisions at Sea (COLREGS). On this basis, an automatic collision avoidance strategy for the encounter situations of multiple vessels is proposed herein. First of all, a COLREGS-complied evasive action decision-making mechanism is established, which can determine the evasive action from the give-way vessel and stand-on vessel separately. It is worth emphasizing that the situation of vessels against COLREGS is taken into consideration herein. Furthermore, a novel automatic collision avoidance controller of multiple vessels on account of model predictive control (MPC) is devised, which can carry out control action ahead of time and handle the problem of rudder saturation. Finally, the effectiveness of the proposed automatic collision avoidance strategy of multiple vessels is illustrated via extensive simulations.
Bonggil Hyun, Pung-Guk Jang, Kyoungsoon Shin
et al.
Copepods, the dominant member of zooplankton and major grazers of phytoplankton in the pelagic ecosystem, are at risk from exposure to antifouling biocides. To evaluate the developmental toxicity of antifouling biocides (Diuron, Irgarol 1051, Sea-nine 211) and wastewater (from high-pressure water blasting (WHPB) and its MeOH extract (WHPB-MeOH)) in the copepod <i>Paracalanus parvus</i> sl, we investigated the chemical concentration, egg-hatching rate, and nauplius mortality. WHPB samples were obtained through hull-cleaning activities involving WHPB in a dry dock. Among the biocides, Sea-nine 211 had the strongest effects on hatching rates and nauplius mortality, which was followed by Diuron and Irgarol 1051. In the WHPB and WHPB-MeOH samples, there was no significant difference between the experimental groups in terms of the egg-hatching rate; however, WHPB was found to be more toxic in terms of nauplius mortality, suggesting that metals in WHPB may also adversely affect nauplius survival in <i>P. parvus</i> sl. A comparison of the LC<sub>50</sub> results of Sea-nine 211 and WHPB revealed that WHPB had a negative effect on nauplius mortality even at a 100-fold lower concentration. Therefore, if chemical contaminants generated during in-water cleaning activity are discharged continuously into the ports without being properly collected through a post-treatment system, they are expected to negatively impact the population of copepods near the port. Although verification is needed through additional experiments, our results could be used for a baseline study concerning the toxicity of antifouling biocides on marine copepod species.
Polar regions face increasing challenges resulting from the interactions between global climate change, human activities, and economic
and political pressures. As the sea ice extent trends diminish, maritime operations have started increasing in these regions. In this respect,
an international concern has arisen for the shrinking of sea ice, preserving the environment, and passengers’ and seafarers’ safety. The
International Maritime Organization has enforced the Polar Code (PC) for the ships navigating in these challenging Arctic and Antarctic
waters. Polar regions are similar in some aspects but exhibit significant differences in geographical conditions, maritime activities, and
legal status. Therefore, the PC that applies to both regions should be reconsidered, accounting for the differences between the areas for
further development. This study considers the Arctic and Antarctic geographical differences relevant to the PC’s scope. The emphasis is
placed on the changes regarding the sea ice extent and sea ice condition differences in the two regions, which are essential in maritime
safety. This study also addresses the aspects of the PC that need improvement.
Synne Frydenberg, Katie Aylward, Kjetil Nordby
et al.
A vessel convoy is a complex and high-risk operation completed during icebreaking operations in the Arctic. Icebreaker navigators need to continuously communicate with their crew while monitoring information such as speed, heading, and distance between vessels in the convoy. This paper presents an augmented reality user interface concept, which aims to support navigators by improving oversight and safety during convoy operations. The concept demonstrates how augmented reality can help to realize a situated user interface that adapts to user’s physical and operational contexts. The concept was developed through a human-centered design process and tested through a virtual reality simulator in a usability study involving seven mariners. The results suggest that augmented reality has the potential to improve the safety of convoy operations by integrating distributed information with heads-up access to operation-critical information. However, the user interface concept is still novel, and further work is needed to develop the concept and safely integrate augmented reality into maritime operations.
Patricia Mares-Nasarre, Gloria Argente, M. Esther Gómez-Martín
et al.
Armor damage due to wave attack is the principal failure mode to be considered when designing conventional mound breakwaters. Armor layers of mound breakwaters are typically designed using formulas in the literature for non-overtopped mound breakwaters in non-breaking wave conditions, although overtopped mound breakwaters in the depth-induced breaking wave zone are common design conditions. In this study, 2D physical tests with an armor slope H/V = 3/2 are analyzed in order to better describe the hydraulic stability of overtopped mound breakwaters with double-layer rock, double-layer randomly-place cube and single-layer Cubipod<sup>®</sup> armors in depth-limited breaking wave conditions. Hydraulic stability formulas are derived for each armor section (front slope, crest and rear slope) and each armor layer. The front slope of overtopped double-layer rock structures is more stable than the front slope of non-overtopped mound breakwaters in breaking wave conditions. When wave attack increases, armor damage appears first on the front slope, later on the crest and, finally, on the rear side. However, once the damage begins on the crest and rear side, the progression is much faster than on the front slope, because more wave energy is dissipated through the armored crest and rear side.
One aspect of the digital transformation process in the shipping industry, a process often referred to as Shipping 4.0, is the increased digitization of on board systems that goes along with increased automation in and autonomy of the vessel. This is happening by integrating Information Technology with Operation Technology systems that results in Cyber Physical Systems on which the safe operations and sailing of contemporary and future vessels depend. Unavoidably, such highly interconnected and interdependent systems increase the exposure of the vessel’s digital infrastructure to cyber attacks and cyber security risks. In this paper, we leverage the STRIDE and DREAD methodologies to qualitatively and quantitatively assess the cyber risk of Cyber Physical Systems on board digitalized contemporary and future ships. Further, we propose appropriate cyber security baseline controls to mitigate such risks, by applying a systematic approach using a set of criteria that take into account the security requirements; the cyber risks; the possible attacks; and the possibly already existing controls, to select from the list of controls provided in the Industrial Control Systems (ICS) overlay of the NIST Guide to ICS Security. The results are expected to support the decision-making and the design of a security architecture for the cyber-enabled ship.
Beach nourishment along the Mediterranean coast of Israel represents a new approach to mitigate coastal erosion by adding suitable sand to threatened beaches. This ‘soft’ solution has become more environmentally and economically acceptable than traditional ‘hard’ solutions, such as seawalls, revetments, detached breakwaters and groins. Beach nourishment projects have been implemented on the Israeli coast north of Ashdod Port (2011), north of Ashkelon Marina (2015) and in the south of Haifa Bay (2016–2017). The performance of these projects was analyzed and compared with nourishment projects along the Mediterranean beaches of Italy, France and Spain. Despite a lack of detailed documentation on most of the European nourishment projects, they proved more durable than the Israeli projects, which were compromised when the imported sand eventually washed offshore. Key factor for the Israeli projects’ failure include the unsuitable morphology of the beaches; insufficient unit sand volume (m<sup>3</sup>/m—volume of nourished sand per meter of the beach length); and imported sand that was too fine versus native sand. The unique physical conditions of the Israeli coast specifically, its open shelf and straight coastline subject to relatively high waves with a very long fetch—also contributed to the poor durability of the nourishment. To improve durability on future projects: imported grain size should be at least 1.5–2.0 times the native sand; unit sand volume should be 400–500 m<sup>3</sup>/m; and supporting measures should be utilized as appropriate.
[Objective] The parametric rolling is a special instability phenomenon of ship in the wave. The current research proves that the change of the stability parameter when the wave passes through the hull is the reason for the rolling motion of the hull,but the mechanical mechanism is unclear.[Methods] Firstly,based on the equations of heave and pitch coupled motion in inertial coordinates and the equations of roll motion in hull coordinates,a hybrid dynamic model of heave pitch and roll was established; secondly,the proposed method of oscillating strip method was used to calculate the motion of ship parametric rolling numerically,and a criterion for parameter roll was proposed based on the principle of energy.[Results] The research results show that the mechanical mechanism for the occurrence of parametric rolling of a ship is that the energy absorbed by the recovery moment coefficient during the increase of the roll angle is less than the energy released by the recovery moment during the decrease of the roll angle;the criterion is that the phase angle of the first-order harmonic component of the recovery torque coefficient lies within[0, π].[Conclusions] Defining the mechanical mechanism of parametric roll is helpful to understand the physical nature of the parametric roll instability mode. The proposed parametric roll criterion is of reference significance for the development of the second generation intact stability criterion of the ship.