Ship behavior prediction via trajectory extraction-based clustering for maritime situation awareness

This study presents a method in which historical AIS data are used to predict the future trajectory of a se-lected vessel.This is facilitated via a system intelligence-based approach that can be subsequently utilized to provide enhanced situation awareness to navigators and future autonomous ships,aiding proactive col-lision avoidance.By evaluating the historical ship behavior in a given geographical region,the method applies machine learning techniques to extrapolate commonalities in relevant trajectory segments.These commonalities represent historical behavior modes that correspond to the possible future behavior of the selected vessel.Subsequently,the selected vessel is classified to a behavior mode,and a trajectory with respect to this mode is predicted.This is achieved via an initial clustering technique and subsequent tra-jectory extraction.The extracted trajectories are then compressed using the Karhunen-Loéve transform,and clustered using a Gaussian Mixture Model.The approach in this study differs from others in that tra-jectories are not clustered for an entire region,but rather for relevant trajectory segments.As such,the extracted trajectories provide a much better basis for clustering relevant historical ship behavior modes.A selected vessel is then classified to one of these modes using its observed behavior.Trajectory predic-tions are facilitated using an enhanced subset of data that likely correspond to the future behavior of the selected vessel.The method yields promising results,with high classification accuracy and low prediction error.However,vessels with abnormal behavior degrade the results in some situations,and have also been discussed in this study.

Internal solitary wave transformation over the slope:Asymptotic theory and numerical simulation

The propagation and evolution of long nonlinear internal solitary waves over slope-shelf topography is theoretically and numerically studied in a two-layer fluid system of finite depth.The variable Korteweg–de Vries(vKdV)and variable extended Korteweg–de Vries(veKdV)equations are derived for the weak and moderate nonlinear waves,respectively.The numerical method is developed from finite difference/volume(FD/FV)scheme to solve the nonlinear equations.The transformation of solitary waves is observed when they propagate past the slope.The elevation of rear face of the front wave grows with the increase of the slope inclination.The results also show that the transformed waves can be described by the steady solution of the corresponding theoretical model(vKdV,veKdV)by considering the depth condition beyond the shelf.

A brief review on tsunami early warning detection using BPR approach and post analysis by SAR satellite dataset

Tsunami early warning systems have provided to be the extreme importance after the tsunami that hit Japan in March 2011.This research article presents a case study based on the tsunami detection using Bottom Pressure Rate(BPR)measurement and the post the analysis using the SAR datasets.A final decision based system using BPR has been studied to carry out the measurements of tsunami wave parameters.SAR based study has also been carried out for the post tsunami studies.Wiener filters are utilized to remove the speckle noise presents in imagery.Future scope of this work has also been proposed.

Impacts of climate change on seasonal extreme waves in the Northwest Atlantic using a Spatial Neural Gas clustering method

Having estimates of wave climate parameters and extreme values play important roles for a variety of different societal activities,such as coastal management,design of inshore and offshore structures,marine transport,coastal recreational activities,fisheries,etc.This study investigates the efficiency of a state-of-the-art spatial neutral gas clustering method in the classification of wind/wave data and the evaluation of extreme values of significant wave heights(Hs),mean wave direction(MWD)and mean wave periods(T0)for two 39-year time periods;from 1979 to 2017 for the present climate,and from 2060 to 2098,for a future climate change scenario in the Northwest Atlantic.These data were constructed by application of a numerical model,WAVEWATCHIII TM(hereafter,WW3),to simulate the wave climate for the study area for both present and future climates.Data from the model was extracted for the wave climate,in terms of the wave parameters,specifically Hs,MWD and T0,which were analyzed and compared for winter and summer seasons,for present and future climates.In order to estimate extreme values in the study area,a Natural Gas(hereafter,NG)clustering method was applied,separate clusters were identified,and corresponding centroid points were determined.To analyze data at each centroid point,time series of wave parameters were extracted,and using standard stochastic models,such as Gumbel,exponential and Weibull distribution functions,the extreme values for 50 and 100-year return periods were estimated.Thus,the impacts of climate change on wave regimes and extreme values can be specified.

Multiple-solitons for generalized(2+1)-dimensional conformable Korteweg-de Vries-Kadomtsev-Petviashvili equation

This paper studied new class of integral equation called the Korteweg-de Vries-Kadomtsev-Petviashvili(KdV-KP)equation.This equation consist of the well-known fifth-order KdV equation in the context of the Kadomtsev-Petviashvili equation.The newly gathered class of sixth-order KdV-KP equation is studied using the sub-equation method to obtain several soliton-type solutions which consist of trigonometric,hyperbolic,and rational solutions.The application of the sub-equation approach in this work draws attention to the outstanding characteristics of the suggested method and its ability to handle completely integrable equations.Furthermore,the obtained solutions have not been reported in the previous literature and might have significant impact on future research.

Population size estimation of chirp and grunt generating fish and mammals using cross-correlation based technique with three acoustic sensors

Passive acoustic monitoring has the potential to be a useful tool for population estimation of sound-producing fish and mammals(mostly whales).Previous work on population estimates of callers employed a simple cross-correlation technique with recordings from two acoustic sensors,and the current work extends the technique to two configurations of a 3-acoustic sensors array using two different sounds,i.e.,chirps which is commonly generated by damselfish(Dascyllus aruanus),humpback whales(Megaptera novaeangliae),dugongs(Dugong dugon)etc.,species,and grunts which is commonly generated by Japanese gurnard(Chelidonichthys kumu),Grey gurnard(Eutrigla gurnardus),gulf toadfish(O.beta),etc.,species.We compared simulated results from this technique with values determined by theoretical approach.We have found that an increasing number of cross-correlation function(CCF)provide better results using this technique.However,the technique has some limitations including negligence of multipath interference,assuming the delays to be integer.

The load criteria for ship mechanical noise prediction in low frequencies and experimental validation

The loading method of the external excitations generated by the equipment directly affects the predicted result of the mechanical noise which should be the same under different excitation forms for the given equipment.In this paper,general load criteria are proposed to define forces/moments as the standard form and convert other forms of loads in the low-frequency domain.As the most typical form to charac-terize equipment excitation,acceleration load loading methods for different conditions are investigated.The equivalent formula between ideal accelerations and generalized forces establishes the first load cri-terion.The second load criterion is proposed to address the issue of an average acceleration loading,in which the phase and amplitude distribution are both absent,and cannot apply to the load identification.The upper and lower limits of the mechanical noise can be determined by the vibroacoustic transfer func-tion of the three load models,and the energy-averaged value is used to represent the mechanical noise.Furthermore,the third criterion is used to handle the case where the acceleration load is given by the results of a bench test.According to the equipment source descriptor invariance,the conversion method is achieved between the bench test and the real ship based on the transfer function of a load model,and the mechanical noise is predicted by an equivalent energy method.Finally,a three-parameter method to quantitatively evaluate the well-fitting of experimental and numerical results,and the load criteria are well validated by underwater acoustic experiments of an experimental model.

Risk assessment of LNG and FLNG vessels during manoeuvring in open sea

Manoeuvring of a Liquefied Natural Gas(LNG)carrier in open sea at Floating LNG(FLNG)terminals can be associated with several operational risks of potential consequences to human safety,the environment and economy.In this paper,a fuzzy set approach was developed to handle the uncertainty in expert opinions commonly used for qualitative risk assessment studies such as the risk matrix.Risk parameters were modelled using a number of fuzzy sets,and a fuzzy risk value was calculated for several hazardous scenarios at different phases during ship berthing operations.The calculated fuzzy risk values were found to be consistent with the results of the risk matrix technique.©2017 Shanghai Jiaotong University.Published by Elsevier B.V.

Assessment of thermal stratification, stability and characteristics of deep water zone of the southern Caspian Sea

Variations of seawater properties and stratification of water column in the southern deep water zone(470 m depth)of the Caspian Sea were evaluated based on field measured data.Variations of physical characteristics(temperature,salinity,density and sound speed)of seawater mainly were limited to the upper 100 m layers.Below this layer,seasonal changes of seawater parameters were minor.Vertical structure of temperature in the southern Caspian Sea waters was characterized by a significant seasonal thermocline approximately between 20 and 50 m depths in summer with a vertical gradient of around 16℃.Destruction of the thermocline occurred with the general cooling of the sea surface water and deepening of the mixed layer during late of autumn and winter.Frequency of stability in water column often across the upper layers(surface mixed and thermocline)was more than deeper levels.Variations of salinity were around 12.4 PSU in the time of measurements.Structures of thermocline and pycnocline were characterized by a significant homogeneity especially in offshore stations during the year.According to high agreement between density and temperature in the Caspian Seawater,a strong seasonal pycnocline was observed in the position of the thermocline.Furthermore,structure of sound speed variations followed vertical variations of seawater temperature.Variations of chemical characteristics(dissolved oxygen and pH)of seawater mainly were continued from sea surface to near the sea bed in deep water zone.

On similarity solutions to (2+1)-dispersive long-wave equations

This work is devoted to get a new family of analytical solutions of the(2+1)-coupled dispersive long wave equations propagating in an infinitely long channel with constant depth,and can be observed in an open sea or in wide channels.The solutions are obtained by using the invariance property of the similarity transformations method via one-parameter Lie group theory.The repeated use of the similarity transformations method can transform the system of PDEs into system of ODEs.Under adequate restrictions,the reduced system of ODEs is solved.Numerical simulation is performed to describe the solutions in a physically meaningful way.The profiles of the solutions are simulated by taking an appropriate choice of functions and constants involved therein.In each animation,a frame for dominated behavior is captured.They exhibit elastic multisolitons,single soliton,doubly solitons,stationary,kink and parabolic nature.The results are significant since these have confirmed some of the established results of S.Kumar et al.(2020)and K.Sharma et al.(2020).Some of their solutions can be deduced from the results derived in this work.Other results in the existing literature are different from those in this work.

Lattice Boltzmann method for consolidation analysis of saturated clay

The lattice Boltzmann method(LBM)has been widely employed in various areas of practical engineering to solve non-linear problems,due to such advantages as the simplicity of programming and the numerical efficiency.In this paper,a new numerical method for onedimensional(1D)consolidation analysis of saturated clay is proposed on the basis of the lattice Boltzmann method.At first,the lattice Bhatnagar-Gross-Krook(LBGK)model is used for 1D consolidation problem of saturated clay subjected to time-dependent loading under different types of initial and boundary conditions.In addition,the multiscale Chapman-Enskog expansion is applied to recover mesoscopic lattice Boltzmann equation to macroscopic consolidation equation.As a result of the numerical simulation for verification,the numerical results are proved to be in good agreement with the analytical solutions available in previous literature.Through the evaluation of convergence and accuracy,it is demonstrated that the proposed method is more accurate and reliable than the finite difference method(FDM)for 1D consolidation analysis of saturated clay.

Nonlinear roll damping of a barge with and without liquid cargo in spherical tanks

Damping plays a significant role on the maximum amplitude of a vessel’s roll motion,in particular near the resonant frequency.It is a common practice to predict roll damping using a linear radiation-diffraction code and add that to a linearized viscous damping component,which can be obtained through empirical,semi-empirical equations or free decay tests in calm water.However,it is evident that the viscous roll damping is nonlinear with roll velocity and amplitude.Nonlinear liquid cargo motions inside cargo tanks also contribute to roll damping,which when ignored impedes the accurate prediction of maximum roll motions.In this study,a series of free decay model tests is conducted on a barge-like vessel with two spherical tanks,which allows a better understanding of the nonlinear roll damping components considering the effects of the liquid cargo motion.To examine the effects of the cargo motion on the damping levels,a nonlinear model is adopted to calculate the damping coefficients.The liquid cargo motion is observed to affect both the linear and the quadratic components of the roll damping.The flow memory effect on the roll damping is also studied.The nonlinear damping coefficients of the vessel with liquid cargo motions in spherical tanks are obtained,which are expected to contribute in configurations involving spherical tanks.

Novel anlytical solution to the damped Kawahara equation and its application for modeling the dissipative nonlinear structures in a fluid medium

A novel approximate analytical solution to the linear damped Kawahara equation using a suitable hypothesis is reported for the first time.Based on the exact solutions(such as solitary waves,cnoidal waves,etc.)of the undamped Kawahara equation,the dissipative nonlinear structures like dissipative solitons and cnoidal waves are investigated.The obtained solution is considered a general solution,i.e.,it can be applied for studying the properties of all dissipative traveling waves described by the linear damped Kawahara equation.Our technique is not limited to solve the linear damped Kawahara equation only,but it can be used for solving a large number of non-integrable evolution equations related to the realistic natural phenomena.Moreover,the maximum global residual error in the whole space-time domain is estimated for checking the accuracy of the obtained solutions.The obtained solutions can help many researchers in explaining the ambiguities about the mechanisms of propagation of nonlinear waves in complex systems such as seas,oceans,plasma physics,and much more.

Symmetry analysis,closed-form invariant solutions and dynamical wave structures of the generalized (3+1)-dimensional breaking soliton equation using optimal system of Lie subalgebra

Nonlinear evolution equations(NLEEs)are primarily relevant to nonlinear complex physical systems in a wide range of fields,including ocean physics,plasma physics,chemical physics,optical fibers,fluid dy-namics,biology physics,solid-state physics,and marine engineering.This paper investigates the Lie sym-metry analysis of a generalized(3+1)-dimensional breaking soliton equation depending on five nonzero real parameters.We derive the Lie infinitesimal generators,one-dimensional optimal system,and geo-metric vector fields via the Lie symmetry technique.First,using the three stages of symmetry reductions,we converted the generalized breaking soliton(GBS)equation into various nonlinear ordinary differential equations(NLODEs),which have the advantage of yielding a large number of exact closed-form solu-tions.All established closed-form wave solutions include special functional parameter solutions,as well as hyperbolic trigonometric function solutions,trigonometric function solutions,dark-bright solitons,bell-shaped profiles,periodic oscillating wave profiles,combo solitons,singular solitons,wave-wave interac-tion profiles,and various dynamical wave structures,which we present for the first time in this research.Eventually,the dynamical analysis of some established solutions is revealed through three-dimensional sketches via numerical simulations.Some of the new solutions are often useful and helpful for study-ing the nonlinear wave propagation and wave-wave interactions of shallow water waves in many new high-dimensional nonlinear evolution equations.

Analysis of series RL and RC circuits with time-invariant source using truncated M,Atangana beta and conformable derivatives

Complex processes of the physical world require novel and sophisticated mathematical notions to get deep insights.In this research analysis,two standard mathematical models for the series RL and RC circuits having time-invariant sources taken from the discipline of electrical engineering have been investigated with the help of differential operators known with the name of truncated M-derivative,Atangana beta-derivative,and the conformable derivative operators.The exact solutions for these two models have been found in terms of the transcendental exponential function of time under the truncated M-derivative,Atangana beta-derivative,and the conformable derivative operators.The numerical simulations carried out via MATLAB”9.4.0.813654(R2018a)”have been interpreted to explore new behavior for solutions of the models not possible to obtain through standard classical calculus wherein one is restricted to have integer-order derivatives unlike the differential operators used in the present research study.The models under consideration for the three differential operators have been investigated with varying parameters’values including the differential ordersαandβwhereupon the classical case is resumed forα=β=1 andτ=0.

Mathematical modeling of tsunami wave propagation at mid ocean and its amplification and run-up on shore

The paper deals with the study of the mathematical model of tsunami wave propagation along a coast-line of an ocean.The model is based on shallow-water assumption which is represented by a system of non-linear partial differential equations.In this study,we employ the Elzaki Adomian Decomposition Method(EADM)to successfully obtain the solution for the proposed model for different coastal slopes and ocean depths.How tsunami wave velocity and run-up height are affected by the coast slope and sea depth are demonstrated.The Adomian Decomposition Method together with Elzaki transform allows for solutions,without the need of any linearization or perturbation,in the form of rapidly converging series.The obtained numerical results for tsunami wave height and velocity are very close match to the real physical phenomenon of tsunami.

A comparison of two wave energy converters’power performance and mooring fatigue characteristics-One WEC vs many WECs in a wave park with interaction effects

The production of renewable energy is key to satisfying the increasing demand for energy without further increasing pollution.Harnessing ocean energy from waves has attracted attention due to its high energy density.This study compares two generations of floating heaving point absorber WEC,WaveEL 3.0 and WaveEL 4.0,regarding their power performance and mooring line fatigue characteristics,which are essen-tial in,e.g.,LCoE calculations.The main differences between the two WECs are the principal dimensions and minor differences in their geometries.The DNV software SESAM was used for simulations and anal-yses of these WECs in terms of buoy heave motion resonances for maximising energy harvesting,motion characteristics,mooring line forces,fatigue of mooring lines,and hydrodynamic power production.The first part of the study presents results from simulations of unit WEC in the frequency domain and in the time domain for regular wave and irregular sea state conditions.A verification of the two WECs’motion responses and axial mooring line forces is made against measurement data from a full-scale installation.In the second part of the study,the influence of interaction effects is investigated when the WECs are installed in wave parks.The wave park simulations used a fully-coupled non-linear method in SESAM that calculates the motions of the WECs and the mooring line forces simultaneously in the time domain.The amount of fatigue damage accumulated in the mooring lines was calculated using a relative tension-based fatigue analysis method and the rainflow counting method.Several factors that influence the power performance of the wave park and the accumulated fatigue damage of the mooring lines,for example,the WEC distance of the wave park,the sea state conditions,and the direction of incoming waves,are simulated and discussed.The study’s main conclusion is that WaveEL 4.0,which has a longer tube than WaveEL 3.0,absorbs more hydrodynamic energy due to larger heave motions and more efficient power production.At the same time,the accumulated fatigue damage in the moorings is lower compared to WaveEL 3.0 if the distance between the WECs in the wave park is not too short.Its motions in the hor-izontal plane are larger,which may require a larger distance between the WEC units in a wave park to avoid losing efficiency due to hydrodynamic interaction effects.

On the dynamics of the gravitational lifting system in the deep sea mining industry

The dynamics of the gravitational lifting system of the deep sea mining industry is demonstrated in this article.A simplified dynamic model is obtained when gravity,buoyancy and drag force are the major concerns.By quantitative analysis,different variables like bucket size,distribution distance,and filling rate are considered to measure their influence on lifting speed and production rate,which ends up with that the most influential factor is the bucket size,and it has a positive correlation with both the two targets:lifting speed and production rate.Due to the breaking strength of the cable wire rope,a feasible design of such a lifting system should take the tension force into consideration.Hence,the feasibility is also examined and a conclusion is summarized that a combination of the bucket size and the distribution distance should be optimized according to the concrete working conditions.

Evaluation of flow characteristics in an onshore horizontal separator using computational fluid dynamics

In the petrochemical industry,separation of oil from water is a very important process.Wells produce mixtures of gas,oil,and water which undergo a primary stage of separation inside horizontal gravity separators.The performance of these vessels is evaluated by measuring mean residence time(MRT)and residence time distribution(RTD).Although many researchers studied flow characteristics in horizontal separators,limited number of articles exist that discuss separator MRT and RTD with varying water-cuts.In this article,the authors study an experiment using a horizontal gravity separator by previous researchers and perform computational fluid dynamics(CFD)simulations on the same geometry under similar conditions.The simulation results show qualitative agreement with the experiments by previous researchers.As shown by experiments before,CFD results showed that MRT of the organic phase increased with increase in water-cut.In addition,the RTD characteristics show very similar trends between CFD and experimental results.

Fuzzy fault tree analysis of oil and gas leakage in subsea production systems

This paper presents a probabilistic failure analysis of leakage of the oil and gas in a subsea production system using fault tree analysis(FTA).A fault tree was constructed by considering four major areas where the leakages can be initiated.These are:gas and oil wells,pipelines,key facilities and third party damage.Conventional FTA requires precise values for the probability of failure of the basic events.However,since the failure data are uncertain,a fuzzy approach to these data is taken which leads to the so-called fuzzy fault tree analysis(FFTA),a method that employs expert elicitation and fuzzy set theories to calculate the failure probabilities of the intermediate events and the top event through identification of the minimal cut sets of the fault tree.A number of importance measures for minimal cut sets and the basic events have been obtained which helps to identify the nature of dependence of the top event on the basic events and thereby can identify the weakest links that may cause leakage in the subsea production system.