Parameter estimation for a ship's roll response model in shallow water using an intelligent machine learning method

In order to accurately identify the ship's roll model parameters in shallow water, and solve the problems of difficult estimating nonlinear damping coefficients by traditional methods, a novel Nonlinear Least Squares Support Vector Machine (NLS-SVM) is introduced. To illustrate the validity and applicability of the proposed method, simulation and decay tests data are combined and utilized to estimate unknown parameters and predict the roll motions. Firstly, simulation data is applied in the NLS-SVM model to obtain estimated damping parameters, compared with pre-defined parameters to verify the validity of the proposed method. Subsequently, decay tests data are used in identifying unknown parameters by utilizing traditional models and the new NLS-SVM model, the results illustrate that the intelligent method can improve the accuracy of parametric estimation, and overcome the conventional algorithms' weakness of difficult identification of the nonlinear damping parameter in the roll model. Finally, to show the wide applicability of the proposed model in shallow water, experimental data from various speeds and Under Keel Clearances (UKCs) are applied to identify the damping coefficients. Results reveal the potential of using the NLS-SVM for the problem of the roll motion in shallow water, and the effectiveness and accuracy are verified as well

Hybrid method for predicting ship manoeuvrability in regular waves

The ship's manoeuvring behaviour in waves is significantly different from that in calm water. In this context, the present work uses a hybrid method combining potential flow theory and Computational Fluid Dynamics (CFD) techniques for the prediction of ship manoeuvrability in regular waves. The mean wave-induced drift forces are calculated by adopting a time domain 3D higher-order Rankine panel method, which includes the effect of the lateral speed and forward speed. The hull-related hydrodynamic derivatives are determined based on a RANS solver using the double body flow model. The two-time scale method is applied to integrate the improved seakeeping model in a 3-DOF modular type Manoeuvring Modelling Group (MMG model) to investigate the ship's manoeuvrability in regular waves. Numerical simulations are carried out to predict the turning circle in regular waves for the 5175 container carrier. The turning circle's main characteristics as well as the wave-induced motions are evaluated. A good agreement is obtained by comparing the numerical results with experimental data obtained from existing literature. This demonstrates that combining potential flow theory with CFD techniques can be used efficiently for predicting the manoeuvring behaviour in waves. This is even more true when the manoeuvring derivatives cannot be obtained from model tests when there is lack of such experimental data

Effect of Ulinastatin on Early Postoperative Cognitive Dysfunction in Elderly Patients Undergoing Surgery: A Systemic Review and Meta-Analysis

Background: Postoperative cognitive dysfunction (POCD) is associated with neuroinflammation by triggering the systemic inflammatory responses. Related studies have demonstrated that ulinastatin, which is a urinary trypsin inhibitor, inhibited the release of inflammatory mediators and improved postoperative cognitive function in elderly patients undergoing major surgery. However, there are controversial results put forwarded by some studies. This systemic review aimed to evaluate the effect of ulinastatin on POCD in elderly patients undergoing surgery.Methods: We searched PubMed, Embase, Cochrane Library, Web of Science, and Ovid to find relevant randomized controlled trials (RCTs) of ulinastatin on POCD in elderly patients undergoing surgery. The primary outcomes included the incidence of POCD and the Mini-Mental State Examination (MMSE) scores. The secondary outcome was the levels of inflammatory cytokines such as tumor necrosis factor (TNF)-α, S100β, C-reactive protein (CRP), interleukin (IL)-6, and IL-10. RevMan 5.3 was used to conduct the meta-analysis.Results: Ten RCTs were included finally. Compared with controls, ulinastatin significantly reduced the incidence of POCD [risk ratio (RR) = 0.29, 95% CI 0.21–0.41, test of RR = 1: Z = 7.05, p < 0.00001]. In addition, patients in the ulinastatin group have lower levels of TNF-α, S100β, CRP, and IL-6 and higher level of IL-10 in serum following surgery.Conclusion: These findings suggested that ulinastatin can be used as an anti-inflammatory drug for POCD prevention in elderly patients undergoing surgery.Systematic Review Registration Number: CRD42019137449

Zinc Acetate Immobilized on Mesoporous Materials by Acetate Ionic Liquids as Catalysts for Vinyl Acetate Synthesis

Ionic liquid containing active ingredient Zn(CH3COO)2 was loaded in mesoporous silica gel to form supported ionic liquids catalyst (SILC) which was used to synthesize vinyl acetate monomer (VAM). SILC was characterized by 1HNMR, FT-IR, TGA, BET, and N2 adsorption/desorption and the acetylene method was used to evaluate SILC catalytic activity and stability in fixed reactor. The result shows that 1-allyl-3-acetic ether imidazole acetate ionic liquid is successfully fixed within mesoporous channel of silica gel. The average thickness of ionic liquid catalyst layer is about 1.05 nm. When the catalytic temperature is 195°C, the acetic acid (HAc) conversion is 10.9% with 1.1 g vinyl acetate yield and 98% vinyl acetate (VAc) selectivity. The HAc conversion is increased by rise of catalytic temperature and molar ratio of C2H2 : HAc and decreased by mass space velocity (WHSV). The catalyst activity is not significantly reduced within 7 days and VAc selectivity has a slight decrease

Comparative study on ship motions in waves based on two time domain boundary element methods

This paper presents a comparative study on the motions of a ship advancing in waves using two different three-dimensional time domain boundary element methods: a Transient Free surface Green's Function (TFGF) method and a Rankine Higher Order Boundary Element Method (HOBEM). Three models based on the HOBEM are also considered to identify the dominant factors affecting the accuracy of solutions: (i) the N–K model using Neumann–Kelvin (N–K) linearization, (ii) the N–K+DB model using the N–K linearization for the free surface boundary conditions and the double-body (DB) m-terms in the body boundary condition, (iii) the Rankine HOBEM based on DB linearization. The Wigley I and the Series 60 (CB = =0.7) are taken as study objects. The comparisons show that the Rankine HOBEM based on DB linearization is generally more accurate than the Rankine HOBEM with other two models and the TFGF method. The hydrodynamic coefficients are mainly affected by the m-terms, especially at low frequencies; while the influences of different linearizations of the free surface boundary conditions are negligible. Both the m-terms and the leading terms of steady velocity potential reserved in the free surface boundary conditions are important for motion responses, while the influence of the former is stronger than the latter

A hybrid method for predicting ship maneuverability in regular waves

Traditionally, ship maneuvering is analyzed under calm water condition. In a more realistic scenario, such as a ship sailing in waves, the importance of taking the wave effects into account should be stressed. In this context, this paper proposes a hybrid method for predicting ship maneuverability in regular waves by combining a potential flow theory based panel method and a Reynolds-averaged Navier-Stokes (RANS)-based computational fluid dynamics method. The mean wave drift forces are evaluated by applying a three-dimensional time-domain higher-order Rankine panel method, which takes the effects of ship's forward speed and lateral speed into consideration. The hull-related hydrodynamic derivatives in the equations of ship maneuvering motion are determined by using a RANS solver based on the double-body model. Then, the two-time scale method is applied to predict ship maneuvering in regular waves by integrating the seakeeping model in a three degrees-of-freedom MMG model for ship maneuvering motion. The numerical results of a laterally drifting S175 container ship, including the wave-induced motions, wave drift forces, and turning trajectories in regular waves, are presented and compared with the available experimental data in literature. The results show that the proposed hybrid method can be used for qualitatively predicting ship maneuvering behavior in regular waves

Numerical and experimental study on the wave-body interaction problem with the effects of forward speed and finite water depth in regular waves

In this study, a time domain higher-order Rankine panel method is developed and applied to evaluate the wavebody interaction problem in shallow water and regular waves. The hydrodynamic effects of forward speed and finite water depth are accounted for. In order to verify the proposed numerical method, the Duisburg Test Case (DTC) container ship is chosen as a study object. The numerical results of the wave-induced ship motions and the added resistance are validated against the data of model tests, which were carried out in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (FHR) in cooperation with Ghent University (UGent) as part of the SHOPERA project