Investigation of the radiative characteristics of an oil-covered rough sea surface using a modified wave spectrum model

This study proposes a method for retrieving ocean sea surface salinity (SSS) using C/X-band ocean emissivities in coastal regions, aiming to verify the performance of these unconventional frequencies for SSS retrieval in warm, high-salinity-variation coastal oceans. Since C/X-band brightness temperatures are less sensitive to sea surface salinity than L-band brightness temperatures, it becomes particularly important to develop a sophisticated and effective method for extracting salinity-related signals from C/X-band brightness temperatures. To this end, a wind effect correction process is developed to remove rough sea surface emissivity contributions from total emissivity and derive calm sea emissivity from WindSat’s brightness temperatures. The wind-induced effects are modeled with a third-order polynomial. Then, based on emissivity analysis, a weighted combination of C/X-band calm sea emissivities (with parameter λ) is introduced to reduce SST sensitivity. This λ-based combination is used to retrieve SSS in the Bay of Bengal. Based on the triple-match method and buoy data, the salinity retrieval results are verified and compared with the Soil Moisture Active Passive (SMAP) SSS and Argo in situ SSS. The results show that the use of parameter λ reduces the RMS error of SSS by 0.1–0.2 psu. The RMSE of SSS retrieval is about 0.64 psu, which is comparable to the error of SMAP data. Simultaneously, the SSS retrieval accuracy is significantly influenced by offshore distance. At an offshore distance of 100 km, the salinity retrieval error exceeds 1 psu, while when the offshore distance exceeds 500 km, the salinity retrieval error is better than 0.6 psu.

This paper reports a simulation-based investigation of low-radar-cross-section (low-RCS) maritime target detection using a pulse–Doppler radar operating in K-distributed sea clutter environments. The results indicate that heavy-tailed clutter statistics significantly deteriorate the performance of conventional cell-averaging CFAR (CA-CFAR), particularly under low signal-to-clutter ratio (SCR) and nonhomogeneous clutter conditions. Range–Doppler analysis confirms that coherent Doppler integration and MTI filtering increase target-to-clutter contrast; however, substantial residual clutter persists in rough sea states. A comparative evaluation demonstrates that ordered-statistics CFAR (OS-CFAR) consistently provides superior performance, achieving higher detection probability, enhanced robustness to clutter transitions, stable false alarm regulation, and improved threshold stability. At a detection probability of 0.8, OS-CFAR attains an SCR advantage of approximately 2–3 dB over CA-CFAR under severe clutter conditions. The results further reveal the influence of Doppler ambiguity and blind speed effects, highlighting the necessity of jointly considering detection algorithms and waveform design to achieve reliable maritime radar operation.

Abstract Sonar detection and diver surveys represent prevalent methods utilized in current offshore wind practices to monitor scour pits around offshore wind turbine foundations. This monitoring is indispensable for ensuring the safety and longevity of these critical structures. Sonar detection, renowned for its versatility across various water depths, offers the advantage of high-resolution 3D mapping of the seabed. However, it entails significant equipment and operational expenses, with its efficacy susceptible to water turbidity and rough sea conditions. On the other hand, diver surveys enable meticulous inspections, providing invaluable insights. Nonetheless, they are constrained by water depth and weather conditions, rendering them time-consuming and financially burdensome due to labour costs. To overcome these limitations, this paper introduces and validates a new accurate scour pit visual monitoring technique, slated for integration into a foundation maintenance AUV operating on the seabed. The research of this new technique begins with the underwater image enhancement model. Subsequently, YOLOv8n-pose is proposed for detecting the deepest point of the scour pit, achieving 84.1% AP while maintaining lightweight properties. Furthermore, the incorporation of SGBM introduces a novel idea for reconstructing the three-dimensional model of scour pit. Finally, experimental verification tests were conducted in the laboratory. The experiment results demonstrate that the proposed technique can swiftly and accurately detect scour pit depth, achieving a Root Mean Square Error (RMSE) of 5.02 mm. This laboratory-scale validation provides a strong foundation for subsequent testing in real-world offshore environments.

Maritime transport faces increasing pressure to reduce fuel consumption and emissions, yet vessel performance under variable sea states remains difficult to bound reliably. Traditional stochastic and data-driven models provide probabilistic forecasts but lack strict guarantees in extreme or out-of-sample conditions. This study develops a deterministic arithmetic-interval framework that replaces uncertain hydrodynamic parameters and wave forcing with bounded intervals. The vessel’s single-degree-of-freedom heave equation is reformulated as an interval differential equation, and existence and uniqueness of the resulting solution tube are established. Validated numerical techniques-interval Taylor expansions, Picard iteration, and adaptive subdivision-are used to compute tight heave envelopes. An interval energy metric integrates worst-case power demand over a voyage, and a branch-and-bound global optimizer selects control parameters (e.g., speed schedules) that minimize the upper-bound energy while satisfying seakeeping constraints. Two hypothetical Karnataka-coast scenarios (“calm” and “rough” seas) demonstrate the rigor and efficiency of the approach. Computed energy-consumption intervals exactly enclose corresponding Monte-Carlo extremes, confirming tightness without large sample sizes. Rough-sea conditions increase worst-case energy demand by approximately 75% despite negligible heave amplitudes at the micron scale. Sensitivity analysis shows that wave-amplitude uncertainty dominates energy variability, while vessel stiffness and damping have minimal influence. The proposed interval framework eliminates under-coverage of worst-case energy (0% missed extremes) and remains within 3–6% of the tightest Monte-Carlo 99% confidence bands, achieving comparable bound tightness with two orders of magnitude fewer model evaluations than CNN–BiLSTM–Attention and kernel-density-based predictors. Benchmarking against linear heave RAO predictions confirms hydrodynamic consistency. The approach provides decision-makers with mathematically guaranteed bounds, supporting targeted measurement, control, and sustainable maritime operations.

High-speed trimaran vessels experience significant motion instability due to hydrodynamic disturbances, parameter uncertainties, and nonlinear coupling effects, particularly during aggressive maneuvers and rough sea conditions. This paper proposes an Uncertainty-Aware Predictive Motion Control (UA-PMC) framework for a foldable-leg mechanism–assisted trimaran system, aimed at enhancing dynamic stability and motion regulation at high speeds. The proposed control strategy integrates a predictive motion model with real-time uncertainty estimation to compensate for environmental disturbances, structural flexibility, and actuator nonlinearities. A robust cost optimization framework is formulated to minimize motion deviations while ensuring constraint satisfaction of the foldable-leg actuation system. The controller adaptively updates prediction horizons based on uncertainty bounds, enabling improved roll, pitch, and heave suppression. Simulation results under varying sea states demonstrate that the proposed UA-PMC significantly improves motion stability, reduces control effort, and enhances tracking accuracy compared to conventional MPC and PID-based approaches, making it suitable for next-generation high-speed marine platforms.

Consider a team of mobile (aerial, ground, or aquatic) robots for orienteering in a hazardous environment. Modeling the environment as a directed graph, each arc is labeled with a probability that a robot will survive upon traversing it, and each node is labeled with the reward given to the robot team if visited by a robot. The arc-traversal hazards could emanate from e.g ., rough terrain or seas, strong winds, radiation, or adversaries capable of attacking or capturing robots. Each reward represents the utility gained by the team when a robot e.g ., delivers a good, takes an image or measurement, or actuates some process to/of/at a node. We want to obtain the Pareto-optimal set of robot-team trail plans on this graph that maximize two (conflicting) team objectives: the expected (1) team reward and (2) number of robots that survive the mission. This way, a human decision-maker can inspect the reward-survival tradeoffs along the Pareto-front, then make an informed selection of a Pareto-optimal robot-team trail plan that balances, according to his or her values, reward and robot survival. To search for the Pareto-optimal set of robot-team trail plans, we implement bi-objective ant colony optimization, guided by both pheromone and problem-specific heuristics. We solve and analyze three problem instances: a synthetic one on a two-community graph; an information-gathering mission in an art museum; and an item-tagging and -verification mission at an abandoned nuclear power plant. We find that ant colony optimization outperforms or performs indistinguishably from a simulated annealing baseline. Ablating the pheromone trails or heuristics reveals that both are important for guiding artificial ants towards Pareto-optimal robot-team trail plans. By inspecting a sample of Pareto-optimal robot-team trail plans along the Pareto-front, we find robots take the safest trails to visit the nodes assigned to them and visit higher-reward nodes earlier in their trail; multiple robots may plan to redundantly visit the same subgraphs to make the team reward robust to robot failures; and rewards from visiting nodes must be balanced against robot survival.

Abstract Although crisis events have become increasingly frequent in recent years, few studies have examined the changes in employees’ work productivity across different stages of a crisis. To advance theory and research on crisis, we investigated the temporal patterns of employees’ work productivity before, during, and after a crisis event. Drawing on the Conservation of Resources Theory, we proposed that employees’ work productivity undergoes a substantial decline during a crisis, which will gradually slow down over time. We further examined the moderating roles of leader–member communication frequency and organizational tenure, positing these factors as critical in shaping productivity trajectories during crisis adaptation. We analyzed data from 342 team members and 69 team leaders within a high-tech off-campus tutoring company, and our findings substantiated the hypothesized productivity change patterns and boundary conditions. To complement the quantitative analysis, we conducted a qualitative study to unveil the underlying psychological mechanisms driving these changes. Our research contributes to the crisis management literature and offers insights into managing employee productivity during times of crisis.

A clear-sighted view is what is needed in a rough sea.

The article presents a comprehensive study of the influence of ship control parameters-in particular, course, trim, and speed-on the vibration level of ship structural elements and the intensity of underwater noise radiation (URN). This paper considers that the torque fluctuations of the main engine and the uneven rotation of the propeller shaft are significantly amplified in rough seas, especially in the absence of effective course correction and control of the ship's heel and trim parameters. Such fluctuations cause increased stress on the shafting components, the main engine base, and the ship's hull, which, in turn, leads to an increase in structural noise and acoustic stress on the marine environment. Within the scope of this study, an approach to optimizing ship control and monitoring the ship's seaworthiness is reviewed. Changing the ship's course relative to the direction of the wave front, along with correcting the trim and speed of the ship, reduces hydrodynamic flow asymmetry and torsional loads, thereby reducing structural vibrations and underwater noise. Spectral signal processing algorithms, in particular discrete Fourier transform, were used to analyze vibrations, which made it possible to identify the main sources of excitation of low-frequency harmonics associated with the propeller and shaft line. Vibration activity was measured and evaluated in accordance with international standards ISO 6954 and ISO 20283-5, taking into account the criteria for acceptable vibration levels for structural elements and ensuring the viability of ship systems. The results of the analysis formed the basis for the development of recommendations for practical ship maneuvering aimed at reducing the acoustic impact on the environment. The methodology proposed in the article allows for the assessment and reduction of structural vibrations and URN without structural changes, relying solely on effective ship management. The research materials are of practical importance for sea vessel crews, navigation system designers, and automated control system developers. They are also consistent with current IMO requirements for minimizing underwater noise in areas of high environmental sensitivity. The article presents a comprehensive methodology for reducing noise pollution based on a combination of ship management solutions, control of ship seaworthiness, hull dynamic characteristics, and technical control and ship condition standards

The Weddell Sea is one of Earth’s most remote and least studied regions. The region around the Larsen C Ice shelf has been largely inaccessible because of its remoteness, extreme cold, rough seas, ice cover, and deep waters. This study documents the first discovery of maintained nesting sites of Lindbergichthys nudifrons (yellowfin notie) in the western Weddell Sea. Nesting sites were found at all locations surveyed during the Weddell Sea Expedition 2019 onboard the SA Agulhas II using the remotely operated vehicle, Lassie . Unlike previous studies, no significant differences in localised water temperature were detected between nesting sites and surrounding waters, except at one site. Novel nesting patterns, groups of nests close to each other, were discernible throughout the video footage; These patterns are thought to have evolved as a form of group predation protection behaviour. These findings provide critical evidence of unique, structured breeding habitats, fulfilling key criteria for the designation of Vulnerable Marine Ecosystems and strengthening the case for the proposed Weddell Sea Marine Protected Area.

ABSTRACT Amidst intensifying great power rivalry between the US and China, the Australian government has looked to greater cooperation with Southeast Asian countries to navigate a peaceful and prosperous course through the rough seas of this second Cold War. This is an understandable but also problematic direction. Economic and security imperatives have long been intertwined. The challenge now, however, is to understand how so in the new political economy of militarised neoliberalism, and the implications for regional engagement. Otherwise, policy plans have shaky foundations. This argument is prosecuted with an illustrative focus on policies of joint Australia and Southeast Asia cooperation in ‘green’ industries, most advanced with Indonesia. Political economy research reveals how policies of cooperation meant to avoid taking sides in superpower contestation can have starkly different outcomes. Identifying and analysing dominant coalitions of economic and socio-political interest, mediating how official policy is implemented or obstructed, is pivotal to understanding the constraints and possibilities of effective cooperation.

Medical Journals: Slow Boats in Rough Seas.

Abstract Structural integrity of Floating Offshore Wind Turbine (FOWT) is the prominent factor that can affect the whole lifecycle of offshore wind project. In practice, structural health monitoring of FOWT is technically challenging under the harsh sea conditions, especially the limitation of sensor placement for internal force measurement. Therefore, Digital Twin (DT) is an important asset that allows real-time remote monitoring and reflects the real condition on site. Recent DT development based on data-driven approach has been explored in offshore structures force monitoring and forecasting. The existing deep learning-based models lack the expressiveness of the geometrical, structural and material properties. To address the problems in the current industry and the limitation of existing simulation approach, a novel finite element surrogate model of FOWT based on Physics-Guided Graph Neural Network (PhyGGNN) is presented. The aero-hydro-servo coupled simulation results are generated from the software QBlade. The semi-submersible OC4 DeepCwind FOWT is considered under the above rated wind speed, rough sea state and water current condition according to metocean of West of Barra, Scotland. In addition, we present the first application of spatial-temporal GNN approach for solving offshore structural dynamics and accurate real-time prediction of wind turbine tower forces under complex wind, wave and current condition for FOWT. Internal forces prediction can allow the remaining useful life calculation in the next stage of fatigue analysis.

Marine vessels experience motion in six degrees of freedom, particularly during adverse weather conditions such as storms, heavy rain, rough seas, and strong winds. Gyroscopic stabilizers offer a promising solution to mitigate these motions, as they are unaffected by hydrodynamic drag and external factors like seaweed. This study focuses on the development and optimization of the gyro plate, a critical component of the gyrostabilizer system. Five gyro plate models, inspired by a published design from prior research, were created and analyzed using Finite Element Analysis (FEA) in SOLIDWORKS. The methodology included a mesh curvature study to ensure the accuracy of stress, deformation, and strain predictions under static loads. The results demonstrated progressive improvements from Models 1 to 5, with Model 5 emerging as the optimal design. For PLA Pro material, Model 5 achieved the lowest stress (2.18 MPa), minimal deformation (0.618 mm), and reduced strain, enhancing structural efficiency by minimizing stress concentrations and evenly distributing loads. While Models 1 and 2 stood out for their simplicity and cost-effective manufacturability, Model 5 balanced superior performance with high compatibility for 3D printing, requiring minimal post-processing. This study highlights the structural efficiency, reduced displacement, and manufacturability of the optimized gyro plate, paving the way for improved gyroscopic stabilization systems. The findings contribute to more efficient and reliable marine transportation, with potential applications for larger vessels.

This paper proposes novel designs of dual-layer flower-shaped heave plates, featuring both aligned and staggered configurations with three, six, and nine petals. Numerical simulations were conducted to study the hydrodynamic effects of these various heave plate designs integrated with the OC4 DeepCwind semisubmersible floating offshore wind turbine platform under prescribed heave oscillations. The overset mesh technique was employed to treat the floating platform’s motions. Comprehensive assessments of vertical force, radiated wave patterns, vorticity fields, added mass, and damping coefficients were conducted. The results revealed that the novel flower-shaped staggered heave plates significantly outperformed conventional circular plates in terms of damping coefficients. Specifically, the damping coefficient of flower-shaped staggered heave plates was greater than that of circular heave plates, while the aligned configuration exhibited a lower damping coefficient. The damping coefficient increased with a reduction in the number of petals for the staggered heave plates. Among the evaluated designs, the dual-layer flower-shaped staggered heave plates with three petals demonstrated the highest effectiveness in attenuating heave motion of the floating platform. The utilization of novel dual-layer flower-shaped staggered heave plates is therefore a promising practice aimed at damping the heave motion of platforms in rough seas.

Abstract To address the challenges of low positioning efficiency, difficulty, and high risk in the hoisting and positioning of a slender-beam payload (SBP) under rough sea conditions, a human-machine cooperative lifting method (HMCLM) is proposed for the first time. In this approach, the operator collaborates with a multi-tagline anti-sway and positioning system (MTAPS) to achieve the rapid and precise positioning of the SBP. A dynamic model of the MTAPS is developed based on multibody dynamics and classical Newtonian mechanics; it also considers the operator’s safety requirements. Simulation analysis is conducted using MATLAB/Simulink, and the results indicate that the HMCLM achieves approximately a 10% improvement in sway reduction compared to the MTAPS. Furthermore, the experimental results demonstrate that the MTAPS achieves an average sway reduction of 89.7% for the double-pendulum system. The proposed HMCLM enables the rapid and precise offshore positioning of the SBP, offering a novel approach to enhancing the efficiency of offshore hoisting operations.

ABSTRACT This article offers an analysis of Turkish maritime identity (MI) construction in the Eastern Mediterranean Sea, and explores how it shapes a state's foreign policy and position. It develops a Middle Power Maritime Typology (MPM) and examines Turkey as a middle power, focusing on its MI and assesses the changes and continuities of it over time and the impact of this newly constructed identity on Turkey's role as a security and peace actor in the region and beyond. Since 2016, Turkish MI has developed through a dynamic interplay of top-down government initiatives and bottom-up demand connections with the sea.

Safety assessment of framed hot launch departure for sea-based rockets in rough sea conditions

ABSTRACT Ship rolling in rough seas, especially with large amplitudes, poses significant challenges in predicting nonlinear damping and restoring forces that influence stability. To enhance modeling accuracy, this study introduces a novel analytical method – Bipartite Polynomial Approximation Method (BPAM) – grounded in the independence polynomials of complete bipartite graphs. The paper formulates and solves a nonlinear second-order differential equation describing ship roll motion under both linear-plus-quadratic and linear-plus-cubic damping situations, without external wave excitation. Additionally, the Bernoulli Wavelet Method (BWM) is employed as a comparative spectral approach. The proposed BPAM effectively converts the nonlinear differential equation into a solvable algebraic system using operational matrices. Key results demonstrate that BPAM yields highly accurate solutions, comparable to those obtained by BWM, Homotopy Perturbation Method (HPM), and classical Runge–Kutta simulations. The study confirms BPAM's computational efficiency and effectiveness in modeling complex roll dynamics, offering practical value for real-time prediction and ship design evaluations.