Grounding Accidents Research Articles

Floquet prethermal order by disorder

Frustrated magnets can have accidental ground state degeneracies which may be lifted by various forms of disorder, for example in the form of thermal or quantum fluctuations. This order by disorder (ObD) paradigm is well established in equilibrium and here is generalized to Floquet many-body systems. Investigating a periodically driven XXZ-compass model on the square lattice, we show that in a prethermal regime, dynamical fluctuations induced by high-frequency drives select a discrete set of states out of a degenerate ground state manifold of the lowest order Floquet Hamiltonian chosen as initial states. Remarkably, prior to the ObD selection, an unusual fluctuating regime emerges leading to a prethermalization timescale scaling linearly with the drive frequency. We argue that prethermal ObD with its unusual approach to the selected states is a generic phenomenon of driven frustrated systems and confirm it in the paradigmatic J1−J2 XX model. Published by the American Physical Society 2024

Design and Implementation of a Shipborne Echo Sounder Simulator Based on a Seabed Echo Scattering and Noise Model

The Manila Amendment 2010 to the STCW International Convention has made clear requirements for seafarers to use the navigation simulation system for training. A shipborne echo sounder is an important navigation aid equipment necessary for a ship’s bridge. Proper use of this equipment can effectively prevent ship grounding accidents. Given the lack of research on simulating different seabed substrate echoes within echo sounder simulations, this paper proposes an algorithm for generating echoes and clutter from various seabed substrates, based on the Jackson model and noise model. Using the seabed echo generation algorithm, the bathymetric data and seabed echo under the influence of ship rolling are generated, the seabed echo simulation of the sounder under the influence of four different grazing angles and six different substrates is realized. Clutter images, including random noise, bubble interference, co-frequency interference, and fish school interference, are also simulated. A typical ship echo sounder simulator is designed and developed. The echo sounder simulator developed in this paper has high realism in seabed echoes and clutter simulation, complete functions, and friendly human–computer interaction. The system has been used by college students and crews, with satisfactory results, which can effectively meet the needs of actual training of seafarers.

Dynamic response analysis of ship reef hard grounding

Abstract With the rapid growth of the world economy, the shipping industry has developed rapidly on a global scale, and the water traffic has become increasingly busy. Therefore, the risk of ship transportation has become bigger and bigger, and ship grounding and collision occupy about 50% of the total number of all accidents, among which the consequences of oil tanker grounding accidents are more serious, which not only jeopardize the safety of the personnel but also cause a large area of pollution to the sea. Therefore, it is particularly important to study the ship grounding and collision of oil tankers. Based on the nonlinear finite element software ABAQUS, a calculation model for oil tanker grounding is established, and simplified boundary conditions that can be used for grounding simulation analysis are determined. At the same time, material strain rate sensitivity and material hardening properties are considered. Based on the quasi-static tensile test data of Q235 steel used in ships, material parameters that meet the requirements of collision simulation calculation are calibrated and calculated. The dynamic response of hard grounding is analyzed from both external and internal mechanisms. The research results can provide a reference for improving the grounding collision performance of oil tankers.

Framework for process risk analysis of maritime accidents based on resilience theory: A case study of grounding accidents in Arctic waters

The complexity and non-linear interactions involved in maritime accidents make it challenging to apply traditional models of risk analysis to them. Resilience is adopting a perspective focuses on holistic aspects of safety across the pre-accident, mid-accident, and post-accident phases. This paper proposes a framework for process risk analysis of maritime accidents based on resilience theory by applying the function resonance analysis method (FRAM). We first identify a three-layer maritime accident based on maritime accident investigation reports and then analyze the potential variability of all relevant functions. Subsequently, a FRAM model is constructed to analyze the accident's functional resonance of accidents by aggregating variations in the functions. Finally, we apply Monte Carlo simulations to compute the values of coupling of all interconnected functions. The ship grounding accidents in Arctic waters is chosen as the case to demonstrate the proposed framework. The relationships of influence between the functions were analyzed to obtain critical coupling pathways of coupling between them, and a time-weighted PageRank algorithm was used to identify key functions. The results show that the proposed approach can reveal vulnerabilities and instabilities in the system, and enables the proposal of targeted, long-term measures of risk control to enhance its resilience and safety.

Ship grounding simulation with different rock shapes and its verification

ABSTRACT Ship grounding often results in damage to the hull, which poses a threat to structural integrity, ship stability, and human life. To reduce the consequences from ship grounding accidents, it is necessary to investigate the damage mechanism and motion responses of ship grounding. The research’s objective is to carry out experimental validation and perform a series of numerical investigations on the ship dynamic responses in grounding. A simulation based on the Coupled Eulerian–Lagrangian(CEL) method was carried out to reproduce a grounding test case conducted in a water tank. It was demonstrated that the numerical results are in good agreement with the experimental results. Then, based on the verified simulation technology, the influences of rock shapes and friction on the grounding damage and motion responses of ships were investigated and discussed. The dynamic response analysis of ships in different grounding scenarios can provide a reference for grounding damage prediction.

Multi-point synchronous temporary grounding wire detection device based on convolutional neural networks

To prevent grounding accidents caused by forgetting to remove the temporary grounding wires and the contact of trees with the distribution network, a multi-point synchronous temporary grounding wire detection device based on convolutional neural networks is developed. The developed device can judge the type of groundings on the test line quickly and locate the ground points accurately during the cut-out. Three-phase alternating current (AC) signals with a specific frequency are injected at multiple points on the line by multiple groups of the device controlled by Raspberry Pi 3B + and embedded Android. The device can achieve the approximate location through the impedance ranging method and the accurate location by integrating the data from multiple points. The trained EfficientNet-B0 algorithm is utilized to predict the grounding positions. The tested results of the prototype verify the accuracy and rapidity of grounding diagnosis and positioning.

Epidemiologies of Fatal Ground Level Falls in Autopsies Conducted in A Tertiary Care Hospital: A cross sectional Study

Background: Falls are the second leading cause of unintentional injury deaths worldwide. Falls not only causes Mortality, but also Morbidity resulting in disabilities and loss of productivity. Death due to falls not only occurs in victims falling from a height but also in Ground level falls.Aim: To study the age and sex distribution, place, surface, time, and outcome of fatal accidental Ground LevelFalls.Methods: The present study was carried out as a descriptive study in which medico legal autopsies of 115 victims of ground level fall victims were included. Lettule’s method of en masse removal of viscera and dissection of organs was used for conducting medico legal autopsy. The Collected data was entered in MS excel and analysed.Conclusion: The current study revealed that most victims of ground level falls were more than 50 years of age and indoor falls were more common than outdoor falls.62% of the victims had suffered head injury. Effective fall prevention programmes should be framed to reduce the number of people who fall.

Risk-based path planning for preventing collisions and groundings of maritime autonomous surface ships

In this paper, we propose and demonstrate a method for risk-based path planning, generating risk-acceptable trajectories for an autonomous surface ship. This objective is achieved in two steps. The first step uses a dynamic probabilistic risk assessment method called K-shortest-paths Probabilistic Risk Assessment (KPRA), alongside risk models and dynamic system simulation, whose output is a list of paths ranked with respect to risk. Multiple risk influencing factors and accident types may be considered in this step. In this work, collision and powered grounding accidents, and their risk-influencing factors and indicators, are considered. The second step is to perform risk evaluation on the ranked scenarios, comparing them to predefined risk acceptance criteria and defining which scenarios have acceptable risk. Evaluating multiple paths allows operators to choose how strict the autonomous ship’s decision-making should be regarding risk, avoiding the problem of minimization algorithms being too conservative in terms of risk. One of the risk-acceptable paths is then chosen as a local plan to be acted by the autonomous ship. This paper has two main scientific contributions. First, an online Bayesian belief network risk model for navigation accident probability is designed and integrated to improve KPRA. Second, we propose a modified guidance, navigation, and control framework for autonomous ships, to include risk-based planning. We implement the modified framework into a real autonomous surface vehicle (ASV) named Grethe and demonstrate the method’s capabilities in field trials, where the ASV uses the method to generate local plans that avoid possible collision and grounding accidents.

Analysis of the impact of Suez Canal blockage on the global shipping network

This study aims to quantitatively analyze the impact of the Suez Canal blockage on global maritime transportation networks. The Suez Canal, a critical global maritime transport route, experienced a significant disruption due to a ship grounding accident in March 2021, exposing the fragility of global logistics supply chains. We constructed a comprehensive shipping network, integrating real trajectory data from automatic identification system (AIS) devices on ships collected in 2018. The network comprises 2713 nodes and 137,830 links, with defined targeted (Suez Canal blockage) and random attack modes. Our analysis, based on multiple network topology metrics, reveals that the blockage had a considerable effect on the global shipping network, significantly more than random disruptions of comparable scale. The incident led to a decrease in network accessibility and connectivity, conforming to the law of distance attenuation. The effects varied across continents; Africa experienced the most significant impact, while Asia and Europe were less affected. Europe's developed transport system effectively mitigated the impact. Data on different ship types passing through the Suez Canal showed that container ships and petrochemical tankers were the most affected. This research underlines the Suez Canal's significance to global shipping and the necessity of robust supply chain management strategies to limit the fallout from similar future incidents.

Study Case of Marine Propulsion Shaft Measurements by the Strain Gage Method: before and after a ship hull grounding accident

The strain gage method for propulsion shaft bending moment verificationhas been in use since the 80’s. In this work, the authors present theirprocedure and results of this method to an Anchor Handling Tug Supply(AHTS) ship. The method was applied in this ship in two occasions: afterdelivery in 2018 and after a grounding accident in 2019. After a period ofhull repair, the bearing reactions were verified at the same time by Jackupand Strain Gage methods. The results by the Strain Gage techniqueare considered more accurate and complete than those of the Jack-up.Based on the Strain Gage results, it was concluded that the groundingaccident caused a change in the alignment of the shaft lines, mainly onstarboard side. The comparison between the methods presented thesame graphic shape, however the Jack-up measurements differed fromthe Strain Gage ones at some points due to some factors noted anddiscussed by the authors.

A two-way coupled FSI ship hard grounding dynamics model

In the maritime sector, ship grounding incidents continue to be a serious problem that may lead to oil spills, capsizing, severe property damage, and even fatalities. Grounding accidents are currently understood utilizing inadequate statistical datasets, probabilistic grounding scenarios, and deterministic computational crashworthiness methodologies due to a lack of practical tools and techniques. The implementation of multiphysics assessment techniques is essential for the development of improved ship safety standards. This involves the use of rapid models for structural integrity rules and damage stability regulations. Taimuri et al., (2022) [1] introduced a rapid two-way coupled fluid-structure interaction (FSI) model that seeks to efficiently examine accidental loads following a ship hard grounding event to fulfil such a requirement. The current study offers an overview of the algorithm and its limitations.

Pseudo-Goldstone Modes and Dynamical Gap Generation from Order by Thermal Disorder.

Accidental ground state degeneracies-those not a consequence of global symmetries of the Hamiltonian-are inevitably lifted by fluctuations, often leading to long-range order, a phenomenon known as "order-by-disorder" (ObD). The detection and characterization of ObD in real materials currently lacks clear, qualitative signatures that distinguish ObD from conventional energetic selection. We show that for order by thermal disorder (ObTD) such a signature exists: a characteristic temperature dependence of the fluctuation-induced pseudo-Goldstone gap. We demonstrate this in a minimal two-dimensional model that exhibits ObTD, the ferromagnetic Heisenberg-compass model on a square lattice. Using spin-dynamics simulations and self-consistent mean-field calculations, we determine the pseudo-Goldstone gap, Δ, and show that at low temperatures it scales as the square root of temperature, sqrt[T]. We establish that a power-law temperature dependence of the gap is a general consequence of ObTD, showing that all key features of this physics can be captured in a simple model of a particle moving in an effective potential generated by the fluctuation-induced free energy.

An object-oriented Bayesian network model for the quantitative risk assessment of navigational accidents in ice-covered Arctic waters

Merchant ship operations in the ice-covered Arctic waters may encounter traditional navigational accident risks (i.e., grounding, collision, etc.) and risks from sea ice, such as ship besetting in ice. However, describing, modeling, and quantifying the multiple risks in ice navigation are challenges from maritime risk assessment perspective. This paper proposes an object-oriented Bayesian network (OOBN) model for the quantitative risk assessment of multiple navigational accidents in ice-covered Arctic waters. The OOBN model makes use of the accident database from Lloyd's intelligence and maritime accident investigation reports. The proposed model decomposes navigational accidents into five levels based on accident causation theory: environment, unsafe condition, unsafe act, probability of navigational accident, and consequence of the navigational accident. Consequently, collision, grounding, ship besetting in ice, and ship–ice collision accidents are selected as the cases to interpret the quantitative risk assessment for navigational risk factors identification, risk analysis, and evaluation. The results demonstrate that (1) the risk is the highest in grounding accidents, followed by besetting in ice, collision, and ship–ice collision in ice-covered Arctic waters; (2) unsafe speed and unsafe condition are the critical mutual factors of these four accident scenarios; (3) and the critical risk influencing factors for the specific navigational accidents are identified to propose corresponding risk control options. The proposed OOBN model can be used for quantitative risk assessment of navigational accidents in ice-covered Arctic waters.

The Role of the ECDIS on the Development of Situational Awareness – a Study on Grounding Accidents

The Role of the ECDIS on the Development of Situational Awareness – a Study on Grounding Accidents

Analytical modelling of ship bottom grounding considering combined surge and heave motions

This paper provides a new contribution to the analytical treatment of ship grounding accidents. New formulations are proposed to assess the resisting force of outer/inner bottom plating and transverse floors when the vessel undergoes combined surge and heave motions during the grounding event. Considering shallow and sharp rocks described by parabolic functions, analytical solutions are derived from plastic limit analysis and validated by comparison to non-linear finite element simulations. A failure criterion is also proposed to trigger the rupture of the bottom plating and all the derived closed-form expressions are implemented into an in-house solver. The solver is then coupled to a 6-DOFs external dynamics program, which allows to account for the action of the surrounding water. Resulting tool is first validated on a full scale cruise ship by comparison to finite element results. It appears than although some discrepancies arise, especially in the response of transverse floors after rupture, the bottom damage distribution seems to be well predicted. Finally, the developed tool is used to quickly predict the grounding response of different types of ships and the influence of their mass and hydrodynamic properties on the damage extent is investigated.

Performance Analysis: Using the Northern Sea Route as an Alternative to Traditional Routes

The grounding accident of M/V EVER GIVEN in the Suez Canal causes a catastrophic loss on shipping companies. Alternatively, previous studies have presented encouraging findings of the remarkable benefits of time and cost saving in the Northern sea route (NSR) due to extend the ice-free time and shorten the distance. Ships using the NSR could shorten as much as 40% of the sailing distance from China (Shanghai) to Europe (Rotterdam) compared with the traditional route via the Suez Canal. This paper investigates the economic potential of using the NSR as a cost-effective route in comparison with Suez Canal Route (SCR) between China and Europe. To achieve this target, the study evaluates the net profit for the SCR fleet and NSR fleet by involving the factors, e.g., bunker price, ice condition and ship loading rate, etc. The case-study results show that the NSR fleet is not profitable compared to the SCR, due to the limited cargo transport capability and ice restriction. Only if the loading rate for SCR fleet is lower than some threshold value or the bunker price is high enough, the NSR turns to be profitable.

The Effect of Dynamic Fracture Strain on the Structural Response of Ships in Collisions

As ship collisions and grounding accidents lead to human injury and damage to the environment and property, more accurate predictions of structural damage to ships under impact loads are needed. Currently, to determine structural behaviors, finite element analysis (FEA) is frequently adopted. However, it is recommended to pay attention to material properties in FEA because structural damage is sensitive to material properties such as yield strength, fracture strain, etc. While the strain rate (impact speed) is automatically considered for dynamic yield stress using the Cowper–Symonds equation or other methods, the pre-defined fracture strain is generally used as the dynamic fracture strain (DFS), which is not dependent on strain rate during the simulation. This assigned value of fracture strain may affect the extent of damage and structural response. In this study, the effect of the DFS on the structural damage from collisions was investigated to determine the relationship between the DFS and damage. Empirical formulas based on predictions of damage by various events were developed as a function of the DFS and initial impact speed. The results of this study explained the effect of the DFS on the structural damage and determined the upper and lower bounds of damage by collisions.

Research on intelligent photovoltaic control and protection switch based on fuzzy PID controller

In recent years, intelligent electrical equipment has been widely used. Control and protection switches (CPS) have the functions of circuit breakers, relays, disconnectors and many other products, etc. The intelligent PV low-voltage switch based on fuzzy PID controller designed in this study is applicable to the low-voltage PV distribution network with rated voltage of 500V and rated current up to 1200A with direct grounding of the neutral point of three four wires. The intelligent photovoltaic low-voltage switch designed in this paper can provide indirect contact protection to the distribution network, which can reduce the occurrence of grounding accidents caused by equipment insulation damage; the intelligent photovoltaic low-voltage switch designed in this paper is equipped with a wireless transmission module, which applies the wireless communication technology to the power equipment, so that the power equipment can realize the functions of remote monitoring the operation status of the power grid and controlling the switch breaking and closing. Finally, the fuzzy PID controller is introduced to improve the reliability of switch operation.

A fast simulation tool for ship grounding damage analysis

This paper presents a numerical tool based on analytical formulations for rapid assessment of damage in ship grounding accidents. Through a step-by-step solution, the ship resistant force is assessed by the super-element method and transferred to a 6-DoF external dynamics solver, which updates the global ship motion by taking into account the action of hydrodynamic forces. The two-way coupled solver is first confronted to finite element simulations considering a 34-kTons cruise ship in bottom and side grounding situations. It is then used to simulate thousands of scenarios, varying the rock shape, the ship impact location, initial penetration and velocity as well as rock/hull friction coefficient. In this way, the influence of ship structural properties (shell thickness, material grade, etc.) on the breach size is investigated. The highest breach reductions are obtained by increasing either the outer shell thickness or the material grade, while acting on transverse frames marginally affects the damage extent. It also appears that a bottom impact is systematically more damaging than a side impact, all else being equal. Likewise, a structural reinforcement is demonstrated to be more efficient in bottom grounding than in side grounding. This is because in side grounding situation, the ship is pushed away by rock and thus undergoes significant sway, yaw and sometimes roll motions that limit the damage extent. Finally, friction is shown to be of primary importance in bottom grounding, while its effect is rather limited in side grounding.

A framework for quantitative analysis of the causation of grounding accidents in arctic shipping

The melting of Arctic Sea ice has significantly facilitated Arctic shipping. However, such increased shipping has brought about higher maritime accidents in Arctic waters, especially for grounding and fire/explosion accidents. The paper presents a framework for quantitative analysis of the causation of grounding accidents in Arctic shipping by developing an accident map (AcciMap) - Bayesian network (BN) model. First, the potential risk factors for grounding accidents in the Arctic shipping were identified according to 322 maritime accident investigation reports (MAIRs) - 299 global MAIRs of grounding accidents (including 5 in Arctic waters) and 23 MAIRs (except grounding accidents) in Arctic waters and related literature. Consequently, an AcciMap model is developed for describing the evolution of grounding accident scenarios and reflecting the interdependency of the identified risk factors. Then, a probabilistic model is proposed to evaluate the probability and severity of the grounding accident for presenting a convincing justification for risk control options (RCOs). The framework is applied for the quantitative analysis of a cruise ship grounding accident in Arctic waters. Results demonstrate (1) improved understanding of cruise ship grounding risk factors related to government supervision, shipping company management, technical and operational management, unsafe incidents and behaviors, and environmental conditions; (2) quantitative analysis of the evolution of grounding accident and better identification of the critical risk factors; (3) determination of RCOs for risk management in Arctic shipping.