In the rapidly advancing field of geological oceanography, the Pacific Ocean and its marginal basins—encompassing key regions like the Sea of Japan, Bohai Bay Basin, South China Sea, and western Pacific seamounts—serve as a critical arena for unlocking Earth’s marine geological mysteries and resource potential [...]
The aim of the study was to examine the implications of the transport process of dangerous goods (DG) by sea on Ro-Ro and Ro-Pax vessels, with particular emphasis on the practical application of the International Maritime Dangerous Goods (IMDG) Code. The research focuses on legal frameworks, operational requirements, and safety procedures, addressing the problem of how effectively IMDG regulations are implemented in daily maritime practice.The study employs legal regulation analysis, process modelling on the Gdańsk– Nynäshamn route, statistical evaluation of 2024 voyage data, and qualitative data from shipowner documentation and expert interviews. Methods include the Delphi approach and FMEA risk analysis. The findings indicate recurring errors in Dangerous Goods Notes (DGNs), such as missing UN numbers, hazard classes, or “marine pollutant” designations. Statistical results show that Class 9 materials, especially lithium-ion batteries, dominate DG shipments, while correlation analysis highlights potential risks when certain classes are transported together. FMEA results point to improper storage and documentation deficiencies as the most significant hazards. The study concludes that compliance with IMDG standards ensures a high safety level, but continuous improvement is required. Enhancing documentation accuracy, crew training, and monitoring systems, along with adapting regulations to new technologies, is essential for safer and more efficient DG transport on Ro-Pax vessels.
Naval Science, History (General) and history of Europe
Nguyen Thi Huyen Trang, Taiga Mitsuyuki, Yoshiaki Hirakawa
et al.
This study investigates the seakeeping performance of a wind power generation ship (WPG ship). This type of vessel uses rigid sails for propulsion and submerged turbines in the form of either two or four booms to generate energy. The research includes both tank tests and simulations using Ansys AQWA, validated with the new strip method (NSM). The vessel used in this study is the container ship KCS. Overall, the power generator increases the ship’s stability and reduces roll but has almost no impact on pitch. The findings show that the 4-boom configuration offers better stability and seakeeping than the 2-boom configuration. The ship’s speed has a significant impact on the ship’s RAO, especially roll and pitch, both for the bare hull and the hull with power generation equipment. When the ship’s speed increases slightly, the roll RAO tends to decrease, but as the speed becomes higher, the RAO tends to increase. Wind conditions notably increase the roll RAO peak, reducing stability, while pitch changes are minimal. The KCS model maintains operational capability in winds up to Beaufort scale 11.
To tackle the problem of existing underwater vehicle covert path planning methods ignoring ambient noise fields, an automated path planning method based on a statistically characterized environmental noise field is proposed. The method involves constructing a background noise spectrum level model using Automatic Identification System (AIS) data and wind speed data. Then, a Range-Dependent Acoustic Model (RAM) is integrated to generate a statistically significant 10th percentile noise field. The result is subsequently incorporated into the sonar equation to develop a noise-considerate concealment effectiveness model, which serves as input for a noise-considerate A* path planning algorithm. Comparative analyses of path planning results demonstrate that, within the studied maritime domain, the noise-prioritized path exhibits a statistically significant reduction in the median detection range by approximately 17%, a 50% reduction in the minimum detection range, and a 20% reduction in the maximum detection range, relative to alternative paths planned with a fixed noise level assumption.
AbstractThis paper optimizes condition‐based replacement policies for a mission‐oriented system. The key challenge in our problem is that the system does not work under a fixed mission type but is subject to an infinite sequence of random types of missions assigned in a Markovian manner, which is realistic in many practical situations. The mission process modulates the deterioration process. Taking advantage of the opportunities when missions are switched, condition monitoring is conducted to support replacement decision‐making. This paper considers two practical scenarios in which the type of the next mission is either available or unavailable at each decision epoch. The objective is to determine the optimal replacement decisions for both scenarios that minimize their long‐run expected average cost rates. The optimization problems are analyzed in the framework of the Markov decision process. The optimal decisions of both scenarios are proven to be of partially monotone control‐limit forms. Near‐optimal policies with multilevel thresholds are provided for more convenient decision‐making. The policy iteration algorithm is modified for efficient optimization. A numerical example is used to demonstrate the feasibility of the proposed approach.
Ocean salinity plays an important role in oceanographic research as one of the fundamental parameters. An optical salinometer based on the Michelson interferometer (MI) suitable for in situ measurement in deep-sea environments is proposed in this work, and it features real-time calibration and multichannel multiplexing using the frequency modulated continuous wave (FMCW) technique. The symmetrical sapphire structure used to withstand deep-sea pressure can not only achieve automatic temperature compensation, but also counteract the changes in optical path length under deep-sea pressure. A model formula suitable for optical salinity demodulation is proposed through the nonlinear least squares fitting method. In vertical profile testing, the optical salinometer demonstrated remarkable tracking performance, achieving an error of less than 0.001 psu. The sensor displays a stable salinity demodulation error within ±0.002 psu during a three-month long-term test at a depth of 4000 m. High stability and resolution make this optical salinometer have broad development prospects in ocean observation.
Selma Aprilla Kardinan, Sedarnawati Yasni, Slamet Budijanto
et al.
Bioactive peptides are promising functional ingredients. Due to its high protein content, snakehead fish (Channa striata) extract (SHFE) is one of the suitable parent proteins for bioactive peptides. This study aimed to investigate the production of SHFE-based antioxidative peptides in a conventional batch and continuous system facilitated by an enzymatic membrane reactor (EMR). The effects of different proteases (Alcalase, Neutrase), substrate concentrations, and enzyme-to-substrate ratios were investigated in the batch process. Continuous hydrolysis was then performed under the optimum conditions obtained from the batch process. The optimum conditions based on the antioxidant capacity measured by DPPH and FRAP assays were employing Alcalase with a substrate concentration [S] of 3% (w/v) and an enzyme-to-substrate ratio [E]/[S] of 10% (w/w). Continuous operation was shown to have been performed over a prolonged period, based on the calculated fouling rate. Furthermore, filtration of the resulting permeate with a smaller membrane pore size (2-kDa) increased the antioxidant capacity. This study is expected to increase the production of functional ingredients in snakehead fish.
The Volume of Fluid (VOF) method is used in two-phase fluid flow problems of ship hydrodynamic calculations, to capture the motion and distribution of the gas–liquid free surface. To ensure solution stability and accuracy, numerical simulations typically require separate mesh refinement for the free surface or a reduced time step, resulting in a significant increase in solution time. This study aims to compare the drag and vessel attitude change calculations of the VOF implicit multi-step method with the traditional single-step method, and to verify the feasibility of the method in the numerical prediction of ship resistance and flow field analysis. The results show that an implicit multi-step method with a reasonable number of internal iterations could obtain results close to those of the single-step method with a reduced time step, and the error in trim angle was relatively large, about 2%, but the solving time was only about half that of the latter. The method could also capture the shape and location of waves on the hull, especially in the vicinity of the ship, while the distribution of the waves in the far field differed from those in the experiments to some extent.
Svetlana Vasilieva, Karina Shibzukhova, Alexei Solovchenko
et al.
Green microalgae, including those from the genus <i>Lobosphaera</i>, are exploited in various fields of biotechnology to obtain valuable fatty acids (e.g., arachidonic acid (C20:4, ARA)) for the production of infant formulae, food and feed additives. In nature, microalgae frequently exist in naturally immobilized state (as biofilms) with a limited cell division rate and increased stress resilience. In the fields of biotechnology, immobilization of microalgae on artificial cell carriers simplifies biomass harvesting and increases culture robustness and productivity. The choice of a suitable cell carrier is central to biotechnology involving immobilized cultures. Cell carriers based on the natural amine-containing polymer chitosan and synthetic polyethylenimine (PEI) are promising candidates for immobilization of phototrophic microorganisms. This is the first report on the effects of immobilization on PEI and chitosan on the accumulation and composition of polyunsaturated fatty acids, including ARA, in <i>Lobosphaera</i> sp. IPPAS C-2047. Immobilization on PEI increased the ARA percentage in the total fatty acids and ARA accumulation by 72% and 81% compared to the suspended cells cultured in complete or nitrogen-deprived medium 14 days, respectively. Immobilization of <i>Lobosphaera</i> sp. on the chitosan-based carrier reduced the ARA percentage but increased oleic and α-linoleic acid percentages. The mechanisms of the effects of immobilization on the fatty acid profiles of the microalgae are discussed.
Donhyug Kang, Byoung Kweon Kim, Seung Won Jung
et al.
Harmful algal blooms (HABs) are types of phytoplankton overgrowth that adversely affect marine ecosystems and aquaculture resources. One such HAB species, <i>Cochlodinium polykrikoides</i>, occurs irregularly and causes significant damage to the aquaculture industry along the coastal regions of Korea. In this study, we developed and implemented an integrated system to detect and predict HAB occurrences in real time. This system comprises four main components: (1) a real-time detection system utilizing acoustic sensing, ocean weather, water temperature, salinity, and chlorophyll, satellite images, genetic analysis, and optics; (2) a prediction model system based on current and tidal, HAB occurrence, and HAB movement and diffusion models; (3) an additional data based on HAB information of sampling data and HAB information of GPS data, and (4) an integrated information system utilizing data storage servers and a visualization platform. We applied and assessed the efficiency of this integrated system in the South Sea of Korea from 2017 to 2019. Particularly, HABs occurred significantly in 2019, and the system demonstrated the feasibility of detection and prediction under field conditions. Implementing a more advanced integrated detection and prediction system in the field is anticipated to minimize the damage caused by irregular HAB occurrences every year.
Vincent Dorie, George Perrett, Jennifer L. Hill
et al.
A wide range of machine-learning-based approaches have been developed in the past decade, increasing our ability to accurately model nonlinear and nonadditive response surfaces. This has improved performance for inferential tasks such as estimating average treatment effects in situations where standard parametric models may not fit the data well. These methods have also shown promise for the related task of identifying heterogeneous treatment effects. However, the estimation of both overall and heterogeneous treatment effects can be hampered when data are structured within groups if we fail to correctly model the dependence between observations. Most machine learning methods do not readily accommodate such structure. This paper introduces a new algorithm, stan4bart, that combines the flexibility of Bayesian Additive Regression Trees (BART) for fitting nonlinear response surfaces with the computational and statistical efficiencies of using Stan for the parametric components of the model. We demonstrate how stan4bart can be used to estimate average, subgroup, and individual-level treatment effects with stronger performance than other flexible approaches that ignore the multilevel structure of the data as well as multilevel approaches that have strict parametric forms.
Zachary T. Johnson, Nathan Jared, John K. Peterson
et al.
Abstract Glyphosate is a globally applied herbicide yet it has been relatively undetectable in‐field samples outside of gold‐standard techniques. Its presumed nontoxicity toward humans has been contested by the International Agency for Research on Cancer, while it has been detected in farmers’ urine, surface waters and crop residues. Rapid, on‐site detection of glyphosate is hindered by lack of field‐deployable and easy‐to‐use sensors that circumvent sample transportation to limited laboratories that possess the equipment needed for detection. Herein, the flavoenzyme, glycine oxidase, immobilized on platinum‐decorated laser‐induced graphene (LIG) is used for selective detection of glyphosate as it is a substrate for GlyOx. The LIG platform provides a scaffold for enzyme attachment while maintaining the electronic and surface properties of graphene. The sensor exhibits a linear range of 10–260 µm, detection limit of 3.03 µm, and sensitivity of 0.991 nA µm−1. The sensor shows minimal interference from the commonly used herbicides and insecticides: atrazine, 2,4‐dichlorophenoxyacetic acid, dicamba, parathion‐methyl, paraoxon‐methyl, malathion, chlorpyrifos, thiamethoxam, clothianidin, and imidacloprid. Sensor function is further tested in complex river water and crop residue fluids, which validate this platform as a scalable, direct‐write, and selective method of glyphosate detection for herbicide mapping and food analysis.
AbstractThis paper studies a combined replenishment and warehouse size planning problem. A firm (3PW user) decides the replenishment quantities over a finite planning horizon to satisfy the time‐varying demands of a product. The firm has no warehouse and contracts with a third‐party warehousing (3PW) provider for storage space over the planning horizon. In the warehousing contract, the planning horizon is partitioned into a number of sessions, and each session also consists of multiple periods. The firm decides a stationary base storage size (BSS) of each session and has an opportunity to adjust the BSS at the beginning of each session. The firm also has the option to rent additional storage size beyond the BSS by paying higher rental cost in each individual period. We explore structural properties and develop a strongly polynomial‐time algorithm by applying geometric techniques to solve the firm's replenishment and warehouse sizing problem. We also conduct numerical experiments and provide important insights into the 3PW user's decisions and the 3PW contract design.
Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of underpowering. A substantial part of the present article presents a detailed analytical review of general principles laid in the foundation of consistent safety standards in the naval architecture and analysis of the existing IMO manoeuvrability criteria and standards. Possible ways of extension of the existing standards to embrace situations associated with adverse sea and wind conditions are discussed and modification of the present standards related to the directional stability is considered as one of the possible solutions. At the same time, it was found that introduction of additional standards for the ship controllability in wind is justified, and the second part of the contribution is dedicated to developing a theoretical basis useful for devising such standards. This includes obtaining a set of analytical solutions related to the steady motion in wind and analysis of wind-tunnel data which resulted in simple equations for conservative generalized envelopes for the aerodynamic forces which are especially convenient for standardizing purposes. Possible design decisions aimed at augmentation of the ship’s capacity to resist adverse environmental factors are outlined.
Roberto Zonta, Giorgio Fontolan, Daniele Cassin
et al.
Lagoon sediments have heterogeneous structure and texture, contain shells and plants and are often highly bioturbated and disturbed by human activities. In such sediments, the selection of representative cores and the choice of a subsampling strategy are important but difficult. In this study, we examine the usefulness of X-ray computed tomography (CT) for inferring sediment features that will help in making optimal decisions prior to core opening (24 cores from seven lagoons). Various algorithms (intensity projections, slice thickness, axial and sagittal images, CT number profiles and volumetric region of interest) are tested to visualise low- and high-density volumes or objects and to quantify the relations between the average volumetric CT number and the bulk density of the sediment matrix. The CT number is related mainly to water content and indirectly to total nitrogen and <16-μm grain-size fraction (model R<sup>2</sup> = 0.94). The outliers are attributed to a weak correspondence between the fraction of sediment sampled for water content determination and the volume of sediment matrix used for CT number measurements in highly heterogeneous sediment slices. In conclusion, CT is a powerful tool for the initial screening of cores recovered from heterogeneous lagoon sediments. The adequate use of available algorithms may provide quantitative information on various sediment features, allowing the purposeful selection of cores and subsamples for further investigation.
Taisuke Takata, Mayuko Takaoka, Rodolfo T. Gonçalves
et al.
A tank experiment using a flexible multi-column floating offshore wind turbine (FOWT) model in regular waves was carried out to clarify the floater elastic response and its influence on the floater motion. The model motion response from the experiment was compared with the numerical simulations by NK-UTWind and WAMIT codes. The dynamic elastic deformation of the model was also compared between the experiment and NK-UTWind. The experiment observed significant elastic deformation for the decks and columns of the model around the wave period corresponding to the natural period of the structural vibration. Furthermore, comparing the heave response amplitude operator (RAO) between experiments and numerical simulations, a small peak appeared around this period in the experiment and NK-UTWind simulation instead of WAMIT simulation. These results indicated that dynamic elastic deformation affected the heave response of the model. The change in the model rigidity revealed that such elastic deformation could affect the motion response statistics in an actual sea condition if the peak period of the onsite wave spectrum is close to the floater natural vibration period. These investigations indicated the importance of considering the elastic behavior of a FOWT at its design stage.
ObjectivesThe hydrodynamic performance under different bailer conditions based on numerical and experimental methods was investigated. MethodsThe hydrodynamic performance of the seaplane with different displacements under different speeds was studied using an experimental method, and the viscous flow field of the seaplane under three conditions（without bailer, bailer closed, bailer lowered) at different speeds was computed.ResultsThe results show that at the same displacement the total resistance and heave amplitude of the seaplane increase, the trim angle decreases, when the speed increases; with displacement increases, the total resistance, trim angle and heave amplitude of the seaplane increase; while the bailer lowers, the total resistance and heave amplitude of the seaplane increase, the trim angle decreases; the effect on the hydrodynamic performance is not obvious as the bailer closes. ConclusionsThe results of this paper are of great significance to the optimal design of water pumping systems of the seaplane.