Hasil untuk "Naval Science"

Rocío Espada, Liliana Olaya-Ponzone, Estefania Martín-Moreno et al.

The Strait of Gibraltar (SG) is a key biogeographic and ecological corridor connecting the Mediterranean Sea and the Atlantic Ocean, enabling the seasonal migrations of fin whales (<i>Balaenoptera physalus</i>). The objective of this study was to characterize, for the first time, the spatial and temporal exposure of the species to maritime traffic during its migration through the SG, quantifying movement patterns, individual composition, and collision risk to identify critical areas for conservation. Validated observations collected between April 2016 and October 2024, with additional records in January and March 2025, were integrated with EMODnet vessel density layers to assess monthly distributions of sightings, individuals, calves, migration patterns, and behavior. A total of 347 sightings comprising 692 individuals were recorded, revealing predominantly westward movements between June and August. Spatial overlap analyses indicated that the highest exposure occurred both near the Bay of Algeciras/Gibraltar and in the northern half of the Central SG, where cargo ship and tanker traffic coincides with dense migration routes and where injuries have been documented in the field. These findings delineate high-risk areas for fin whales throughout the SG and provide an empirical basis for spatial management measures, including speed reduction zones, adaptive route planning, and the possible designation of the area as a cetacean migration corridor. The proposed measures aim to mitigate collision risk and ensure long-term ecological connectivity between the Mediterranean and the Atlantic.

Lara Mills, Juan L. Garzon, Flávio Martins

Simulating wave propagation is crucial for forecasting processes offshore and near the coast. Many operational wave models consider only atmospheric and wave forcing as boundary conditions. However, waves and currents are interdependent, and simulating their interaction is crucial for accurately representing wave propagation. This study examines the influences of the current velocity and water levels on waves on the southern coast of the Iberian Peninsula. These forcing elements were simulated by a 3D hydrodynamic model (MOHID) and included in the Simulating WAves Nearshore (SWAN) model. The standalone SWAN model was calibrated and validated by comparing results of significant wave height, mean wave direction, and peak period with in situ observations. Then, the effects of water levels and current velocities on wave propagation were assessed by forcing the SWAN model with water levels as well as current velocities extracted from different depths: the surface layer and depth-averaged velocities from the surface down to 10 m, 20 m, and the full water column. The results revealed that incorporating the current velocity and water levels from MOHID into the SWAN model reduced the root mean square error (RMSE) between 1.6% and 27.6%. The most accurate results were achieved with model runs that included both the current velocity from the surface layer and water levels. Opposing currents resulted in increases in wave height, whereas following currents resulted in decreases in wave height. This work presents novel results on the effects of hydrodynamics on wave propagation along the southern coast of the Iberian Peninsula, a region of key importance for the blue economy.

Wenbo Dong, Jiaming Chen, Yufei Zhang et al.

During polar navigation, icebreakers frequently encounter ice ridges, which can significantly reduce navigation efficiency and even pose threats to structural safety. Therefore, studying the ramming of ice ridges by the icebreaker is of great importance. In this study, the ice ridge is decoupled into the consolidated layer and the keel for modeling. The consolidated layer is simplified as layered ice, and an innovative hybrid empirical–numerical method is used to determine the icebreaking loads. For the keel, a failure model is developed using the Mohr–Coulomb criterion in combination with the effective stress principle, accounting for shear failure in porous media and incorporating both cohesion and internal friction angle. The ship is restricted to surge motion only. A comparative analysis with the model test results was conducted to assess the accuracy of the method, with the predicted ice resistance showing deviation of 9.85% in the consolidated ice area and 10.48% in the keel area. Ablation studies were conducted to investigate the effects of different ice ridge shapes, varying retreat distances, and different ship drafts on the performance of ramming the ice ridge. The proposed method can quickly and accurately calculate ice ridge loads and predict their motion responses, providing a suitable tool for on-site rapid navigability assessment and for the design of icebreakers.

Amit Bajpai, Naveen Chidanandaswamy, Bharat Hosur et al.

Persistent craniopharyngeal canal (PCPC) is a rare congenital anomaly arising from the incomplete closure of the craniopharyngeal canal during embryological development. Imaging plays a crucial role in identifying and understanding the anatomical characteristics and guiding appropriate management strategies. We present a series of four cases of PCPC with varied and unexpected clinical presentations along with details of imaging nuances and management implications, emphasizing the importance of radiodiagnosis in guiding appropriate management strategies. From incidental diagnosis in an asymptomatic adult to a symptomatic syndromic child, the PCPC has a wide clinico-radiological spectrum of presentation as well as management challenges.

Tianju Zheng, Liping Sun, Mingwei Li et al.

Artificial island construction is a multifaceted engineering endeavor that demands precise scheduling to optimize resource allocation, control costs, ensure safety, and minimize environmental impact within dynamic marine environments. This study introduces a comprehensive multi-objective optimization model that integrates critical factors such as resource limitations, task dependencies, environmental variability, safety risks, and regulatory compliance. To effectively address the complexities of this model, we develop and employ the Multi-Objective Adaptive Cooperative Evolutionary Marine Genetic Algorithm (MACEMGA). MACEMGA combines cooperative coevolution, adaptive dynamic weighting, dynamic penalty functions, and advanced genetic operators to navigate the solution space efficiently and identify Pareto optimal schedules. Through extensive computational experiments using data from the Dalian Bay Cross-Sea Traffic Engineering project, MACEMGA is benchmarked against algorithms such as NSGA-II, SPEA2, and MOEA/D. The results demonstrate that MACEMGA achieves a reduction in construction time from 32.8 to 23.5 months and cost savings from CNY 4105.3 million to CNY 3650.0 million while maintaining high-quality outcomes and compliance with environmental standards. Additionally, MACEMGA shows improvements in hypervolume by up to 15% over existing methods and a Convergence Rate that is 8% faster than MOEA/D.

Joseph Daiz, Elisa Vinco-Garcia

<p><strong>Purpose:</strong> This study aimed to investigate the teaching strategies, pedagogical competence, and challenges encountered by maritime professional instructors in Maritime Higher Education Institutions (MHEIs) to inform the development of an enhancement program.</p><p><strong>Methods:</strong> A descriptive-comparative design was employed, utilizing a quantitative approach to examine the teaching strategies, pedagogical competence, and challenges faced by 75 maritime professional instructors selected through stratified random sampling. Data were gathered using a researcher-made instrument consisting of four parts, with its validity established through expert validation and reliability ensured via pilot testing using Cronbach's Alpha method.</p><p><strong>Findings:</strong> The results indicated that the most prevalent teaching strategies among maritime professional instructors included quizzes, tests, discussions, demonstrations, hands-on activities, practical exercises, and lectures enhanced by interactive techniques. The instructors exhibited a very high level of pedagogical competence overall and across various categories, including rank, teaching experience, educational attainment, and classification. Nonetheless, they encountered significant challenges such as financial concerns, limited resources and skills, and fatigue stemming from inadequate sleep.</p><p><strong>Research Implications:</strong> The study underscores the importance of a balanced approach that integrates traditional and interactive teaching methods to foster comprehensive learning in maritime education. The high level of pedagogical competence among instructors highlights their effectiveness in facilitating meaningful learning experiences. Furthermore, the findings suggest that factors such as training in instructional methods and industry expertise may be more critical in developing effective teaching skills than conventional indicators like rank, experience, or educational background.</p><p><strong>Practical Implications:</strong> Educational institutions should consider addressing the challenges faced by maritime professional instructors by providing support systems and resources that enhance teaching efficacy and well-being. Additionally, promoting ongoing professional development focused on instructional methods and practical skills can further strengthen the pedagogical competence of instructors, ultimately benefiting student learning outcomes in maritime education.</p><p> </p><p><strong>Received: 05 August 2024 </strong></p><p><strong>Accepted: 02 September 2024 </strong></p><p><strong>Published: 22 September 2024</strong></p>

Lichao Jiang, Zhi Zhang, Lingyun Lu et al.

Ship dynamic models serve as the foundation for designing ship controllers, trajectory planning, and obstacle avoidance. Support vector regression (SVR) is a commonly used nonparametric modelling method for ship dynamics. Achieving high accuracy SVR models requires a substantial amount of training samples. Additionally, as the number of training samples increases, the computational efficiency for solving the quadratic programming problem (QPP) of SVR decreases. Ship controllers demand dynamic models with both high accuracy and computational efficiency. Therefore, to enhance the prediction accuracy and computational efficiency of SVR, this paper proposes a nonparametric modelling method based on twin SVR (TSVR). TSVR replaces a large QPP with a set of smaller QPPs, significantly enhancing generalizability and computational efficiency. To further improve the predictive accuracy of TSVR, the puma optimizer algorithm is employed to determine the optimal hyperparameters. The performance of the proposed method is validated using a Mariner class vessel. Gaussian white noise is introduced into the modelling data to simulate measurement error. The TSVR model accurately predicts various zigzag and turning circle manoeuvring motions under disturbance conditions, demonstrating its robustness and generalizability. Compared to the SVR model, the TSVR model achieves lower root mean square error and computational time, confirming its superior predictive accuracy and computational efficiency.

Xiaodi LIANG, Yindong LIU

ObjectiveTo address the issue of assessing structural breach damage in ships under underwater explosion, a breach prediction method based on the PCA-BOA-KNN model is established. MethodsFirst, finite element models for five-compartment and seven-compartment segments are constructed, and explosion simulation analysis is carried out for 21 sets of underwater explosion conditions. Subsequently, principal component analysis (PCA) is employed to reduce the dimensionality of the peak acceleration, peak velocity, peak displacement, peak stress and peak overpressure values, resulting in two principal features. Finally, the PCA results are integrated into a Bayesian optimization algorithm (BOA) K-Nearest Neighbors (KNN) model. The established breach prediction model is used to predict the breach conditions at different ship cross-sections under a set of conditions. ResultsThe results show that by using PCA to extract the first two factors, the cumulative contribution rate is 85.165%. Therefore, the first two factors can represent the primary information of the five features. The results obtained using the PCA-BOA-KNN breach prediction model are generally consistent with the simulation results. ConclusionThe proposed prediction model approach is effective for predicting ship structural breaches and has reference value for predicting breachs in ship structures with different principal dimensions.

Jian Zheng, Wenjun Sun, Yun Li et al.

In order to solve the multi-objective planning and trajectory tracking control problem related to maritime autonomous surface ships (MASSs), a new design scheme for autonomous navigation is proposed in this paper, with a receding horizon navigation and control (RHNC) system that contains navigation and control modules. In the navigation module, we designed a superposition field gradient descent local search algorithm based on the cost field, emission field, and guidance field to navigate the MASS reference path, and in the control module, we designed a nonlinear controller that can handle multiple constraints based on the NMPC framework. Under the new scheme, the navigation module completes local path planning to reduce costs and emissions, the control module accomplishes accurate trajectory tracking and real-time collision avoidance, and the information is transmitted in both directions between the two modules to collaboratively complete the MASS navigation and control tasks. We conducted a simulation study of the navigation algorithm and controller and the autonomous navigation system using a Kriso Container ship (KCS). The simulation results demonstrate the effectiveness of the proposed cooperative design scheme in reducing navigation costs and emissions and avoiding autonomous collision avoidances.

S. Acharya, D. Adamová, A. Adler et al.

This letter reports measurements which characterize the underlying event associated with hard scatterings at mid-pseudorapidity (|η|<0.8) in pp, p–Pb and Pb–Pb collisions at centre-of-mass energy per nucleon pair, sNN=5.02TeV. The measurements are performed with ALICE at the LHC. Different multiplicity classes are defined based on the event activity measured at forward rapidities. The hard scatterings are identified by the leading particle defined as the charged particle with the largest transverse momentum (pT) in the collision and having 8 <pT<15GeV/c. The pT spectra of associated particles (0.5 ≤pT<6GeV/c) are measured in different azimuthal regions defined with respect to the leading particle direction: toward, transverse, and away. The associated charged particle yields in the transverse region are subtracted from those of the away and toward regions. The remaining jet-like yields are reported as a function of the multiplicity measured in the transverse region. The measurements show a suppression of the jet-like yield in the away region and an enhancement of high-pT associated particles in the toward region in central Pb–Pb collisions, as compared to minimum-bias pp collisions. These observations are consistent with previous measurements that used two-particle correlations, and with an interpretation in terms of parton energy loss in a high-density quark gluon plasma. These yield modifications vanish in peripheral Pb–Pb collisions and are not observed in either high-multiplicity pp or p–Pb collisions.

Suhyeon Park, Jongwon Seok, Jungpyo Hong

Snapping Shrimps (SSs) live in a warm ocean except the North and South Poles, and they are characterized by generating strong shock waves underwater using large claws. Shock waves generated by these SSs are used for marine noise research as a signal and as a noise source, because they cause a decrease in the Signal-to-Noise Ratio (SNR), acting as one of the disruptors in fields such as sonar for target detection and underwater communication. A state-of-the-art technique to detect Snapping Shrimp Noise (SSN) is Linear Prediction (LP) analysis. Using the feature where SSN occurs for a very short time, the SSN interval was detected based on the phenomenon where the residuals appear large in the SSN interval when the LP analysis is used. In this paper, we propose an SSN interval detection technique using the Likelihood Ratio (LR) as a follow-up study to the LP-analysis-based method for further performance improvements. The proposed method was used to analyze the statistical distribution characteristics of the LP residual of SSNs compared to Gaussian, Laplace, and Gamma distributions through the Goodness-Of-Fit test. Based on this, the statistical-model-based LRs of the three distributions were computed to detect the SSN interval. Comparing the proposed method with the state-of-the-art method, the proposed method achieved 0.0620, 0.0675, and 0.0662 improvements in Gaussian, Laplace, and Gamma distributions in the Receiver Operating Characteristic curve and Area Under Curve, respectively. The study results confirmed that the proposed method can operate effectively in the marine acoustic environment. This can help find accurate intervals for the automatic labeling of or reduction in SSN.

P. Swaczyna, N. Schwadron, E. Mobius et al.

On its journey through the Galaxy, the Sun passes through diverse regions of the interstellar medium. High-resolution spectroscopic measurements of interstellar absorption lines in spectra of nearby stars show absorption components from more than a dozen warm partially ionized clouds within 15 pc of the Sun. The two nearest clouds—the Local Interstellar Cloud (LIC) and Galactic (G) cloud—move toward each other. Their bulk heliocentric velocities can be compared with the interstellar neutral helium flow velocity obtained from space-based experiments. We combine recent results from Ulysses, IBEX, and STEREO observations to find a more accurate estimate of the velocity and temperature of the very local interstellar medium. We find that, contrary to the widespread viewpoint that the Sun resides inside the LIC, the locally observed velocity of the interstellar neutral helium is consistent with a linear combination of the velocities of the LIC and G cloud, but not with either of these two velocities. This finding shows that the Sun travels through a mixed-cloud interstellar medium composed of material from both these clouds. Interactions between these clouds explain the substantially higher density of the interstellar hydrogen near the Sun and toward stars located within the interaction region of these two clouds. The observed asymmetry of the interstellar helium distribution function also supports this interaction. The structure and equilibrium in this region require further studies using in situ and telescopic observations.

Yaniv Shmuel, Yaron Ziv, Baruch Rinkevich

Canopies of branching corals harbor a wide range of sessile- and mobile-dwelling species that benefit from the physical compartments and the micro-environments created by the complex three-dimensional structures. Although different compartments within canopies are differentially used by inhabitant species, the distribution of mobile animals between coral canopy compartments are not fully explored. Here, we study <i>Stylophora pistillata</i>, a common branching coral in the Gulf of Eilat that harbors obligatory crabs from the family <i>Trapezia</i>. Two in situ surveys elucidated diel dynamics in compartmental distributions of <i>Trapezia</i> species within <i>S. pistillata</i> canopies compartments, associated with the crab’s body size and day/night activities. Whereas all crabs were found within sheltered spaces in the coral canopy understory or in the base during day hours, laboratory experiments revealed that nighttime distributions of small and large crabs (in middle and up compartments, respectively) are not intraspecific competition-borne, but rather, the outcome of preferred crab-size location for a novel feeding type, predation on demersal plankton. This study, thus, disclosed the importance of studying the coral’s three-dimensional structures and within canopies’ compartments for understanding the biology of dwelling species in the animal forests’ canopies.

D. Andrews

As part of writing a short article entitled “Ship Design – From Art to Science?” [1] for the Institution’s 150th anniversary celebratory volume [2], the author consulted the Institution’s centenary book by K C Barnaby [3] to get a feel for the formative first hundred years of ship design recorded in the learned papers presented to the Institution. This consultation was motivated by consideration of the papers in the first volume of the Transactions of 1860, which, surprisingly, contained no papers directly on ship design, either on ship design in general or through describing the design intent behind a specific new ship. Rather, like the very first paper by Reverend J Woolley, the remaining 1860 papers concerned themselves with what could be called the application of science (and mathematics) to the practice of naval architecture as an engineering discipline. However this initial focus broadened out in subsequent volumes of the Transactions so that both technical descriptions of significant new ship designs and, more recently, papers on the general practice of ship design have also figured, alongside the presentation of progress in the science of naval architecture. Given that the vast bulk of ships built over this period have been designed like most buildings to a set pattern, or as we naval architects would say based on a (previous) “type ship”, those designs presented in the Institution’s Transactions, and the few other collections of learned societies’ papers, are largely on designs that have been seen to be of particular merit in their novelty and importance. Therefore this review looks at the developments in ship design by drawing on those articles in the Transactions that are design related. In doing so the papers have been conveniently broken down into the three, quite momentous, half centuries over which the Institution has existed. From this historical survey, it is then appropriate to consider how the practice of ship design may develop in the foreseeable future.

Lan Gao, Chiara Dachena, Kaijun Wu et al.

The nondestructive characterization of cylindrical objects is needed in many fields, such as medical diagnostics, tree trunk inspection, or concrete column testing. In this study, the radar equation of Lambot et al. is combined with cylindrical Green’s functions to fully model and invert ultra-wideband (UWB) ground-penetrating radar (GPR) data and retrieve the properties of cylindrical objects. Inversion is carried out using a lookup table (LUT) approach followed by local optimization to ensure retrieval of the global minimum of the objective function. Numerical experiments were conducted to analyze the capabilities of the developed inversion procedure to estimate the radius, permittivity, and conductivity of the cylinders. The full-wave model was validated in laboratory conditions on metallic and plastic pipes of different sizes. The adopted radar system consists of a lightweight vector network analyzer (VNA) connected to a single transmitting and receiving horn antenna. The numerical experiments highlighted the complexity of the inverse problem, mainly originating from the multiple propagation modes within cylindrical objects. The laboratory measurements demonstrated the accuracy of the forward modeling and reconstructions in far-field conditions.

Yueqi HOU, Hao TAO, Junbin GONG et al.

ObjectivesFor achieving navigational safety and continuous communication link between swarms of unmanned marine vehicle (UMV) during mission execution, the cooperative path planning of unmanned surface vehicle (USV) and unmanned aerial vehicle (UAV) swarms is studied.MethodsKeep-in and keep-out geo-fences are used to carry out scene modelling, and the problems of threat and obstacle avoidance are transformed into geo-fence constraints. Aiming at collision avoidance and continuous communication link between vehicles, a judgment criterion for the constraints of collision avoidance and communication link via time sequence detection is proposed. The average travel time (ATT) of the swarm is taken as the path optimization function, and the multiple constraints are transformed into penalty functions. A self-adaptive differential evolution algorithm is adopted to solve the optimization problem.ResultsThe proposed method can ensure safe navigation and communication link between USV and UAV swarms in hostile and obstacle-filled environment, and achieve the shortest ATT under multiple constraints.ConclusionsThis method has practical value for the off-line path planning of UMV swarms in the hostile and obstacle-filled environment.

Mireille Escudero, Jassiel V. Hernández-Fontes, Irving D. Hernández et al.

This paper presents the use of virtual level (VL) probes as an alternative image-based approach to investigate the interaction of waves with coastal structures in wave flume experiments. These probes are defined as regions of interest located at specific positions along the horizontal domain of the images, in which edge interfaces are detected and, thus, their vertical motions can be obtained. To demonstrate the use of the methodology, a critical condition of breaking waves interacting with a Cubipod homogeneous low-crested structure (HLCS) in a two-dimensional framework was selected. With the video recorded from the experiments, image calibration, processing, and analysis stages were implemented to analyze the performance of the HLCS in reducing wave elevations and to study the stability of the armor units. The present approach can be extended to a wide range of coastal structures applications where the interface detection between components of the scene is useful to observe the behavior of coastal structures, increasing effectiveness and alternatives to acquire precise data in 2D experimental tests.

Fareha Hilaluddin, Fatimah Md. Yusoff, Tatsuki Toda

A study on seasonal phytoplankton abundance and composition in a mangrove estuary, Matang Mangrove Forest Reserve (MMFR), Malaysia, was carried out to determine the phytoplankton structure in this ecosystem, and to identify potential indicators of environmental changes. Phytoplankton samples were collected bimonthly from June 2010 to April 2011, to cover both dry (June to October) and wet (November to April) seasons, at four selected sampling sites along the river. Diatoms showed the highest number of species (50 species) from a total of 85 phytoplankton species from 76 genera. Diatoms contributed more than 90% of the total phytoplankton abundance during the dry season (southwest monsoon) and less than 70% during the wet season (northeast monsoon) as dinoflagellates became more abundant during the rainy season. Two diatoms were recorded as dominant species throughout the sampling period; <i>Cyclotella</i> sp. and <i>Skeletonema costatum</i>. <i>Cyclotella</i> sp. formed the most abundant species (62% of total phytoplankton) during the dry period characterized by low nutrients and relatively low turbidity. <i>Skeletonema costatum</i> contributed 93% of the total phytoplankton in October, which marked the end of the dry season and the beginning of the wet season, characterized by strong winds and high waves leading to the upwelling of the water column. Massive blooms of <i>Skeletonema costatum</i> occurred during the upwelling when total nitrogen (TN) and total phosphorus (TP) concentrations were highest (<i>p</i> < 0.05) throughout the year. The abundance of diatom species during the wet season was more evenly distributed, with most diatom species contributing less than 12% of the total phytoplankton. Autotrophic producers such as diatoms were limited by high turbidity during the northeast monsoon when the rainfall was high. During the wet season, <i>Cyclotella</i> and <i>Skeletonema costatum</i> only contributed 9% and 5% of the total phytoplankton, respectively, as dinoflagellates had more competitive advantage in turbid waters. This study illustrates that some diatom species such as <i>Cyclotella</i> sp. and <i>Skeletonema costatum</i> could be used as indicators of the environmental changes in marine waters.

Anna Platta

The presence of fiber in food, especially fermenting fiber, is the basis of a healthy diet, while prebiotics are specialized food ingredients that affect specific bacteria, their final fermentation products, and thus have a beneficial effect on the host's health. The aim of the study was to assess the quantity of consumption of fiber-containing foods by a selected group of women. The study was conducted using the direct survey method among 145 respondents aged over 18 years, residing in the city of Gdynia. By means of the study, it was found that the nutrition behavior of the study group was incorrect, as the frequency of consuming fiber-containing foods was low. Own research and literature studies allow to formulate a statement that healthy people – women living in Poland, do not consume enough dietary fiber in their daily diet. The increase in consumption of products that are sources of dietary fiber by Polish women is very important in terms of improving their well-being and preventing overweight, obesity, diabetes, cardiovascular diseases and gastrointestinal cancer.

Tianlong Mei, Maxim Candries, Evert Lataire et al.

In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed for 3D diffraction and radiation problems. Non-uniform rational B-splines (NURBS) are used to describe the body and free surfaces. The NSWM potential is computed by linear superposition of the first-order and second-order steady wave-making potentials which are determined by solving the corresponding boundary value problems (BVPs). The so-called <i>m_j</i> terms in the body boundary condition of the radiation problem are evaluated with nonlinear steady flow. The free surface boundary conditions in the diffraction and radiation problems are also derived by considering nonlinear steady flow. To verify the improved model and the numerical method adopted in the present study, the nonlinear wave-making problem of a submerged moving sphere is first studied, and the computed results are compared with the analytical results of linear steady flow. Subsequently, the diffraction and radiation problems of a submerged moving sphere and a modified Wigley hull are solved. The numerical results of the wave exciting forces, added masses, and damping coefficients are compared with those obtained by using Neumann&#8722;Kelvin (NK) flow and double-body (DB) flow. A comparison of the results indicates that the improved model using the NSWM flow can generally give results in better agreement with the test data and other published results than those by using NK and DB flows, especially for the hydrodynamic coefficients in relatively low frequency ranges.