Numerical study on hydrodynamics of ships with forward speed based on nonlinear steady wave

In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed for 3D diffraction and radiation problems. Non-uniform rational B-splines (NURBS) are used to describe the body and free surfaces. The NSWM potential is computed by linear superposition of the first-order and second-order steady wave-making potentials which are determined by solving the corresponding boundary value problems (BVPs). The so-called mj terms in the body boundary condition of the radiation problem are evaluated with nonlinear steady flow. The free surface boundary conditions in the diffraction and radiation problems are also derived by considering nonlinear steady flow. To verify the improved model and the numerical method adopted in the present study, the nonlinear wave-making problem of a submerged moving sphere is first studied, and the computed results are compared with the analytical results of linear steady flow. Subsequently, the diffraction and radiation problems of a submerged moving sphere and a modified Wigley hull are solved. The numerical results of the wave exciting forces, added masses, and damping coefficients are compared with those obtained by using Neumann–Kelvin (NK) flow and double-body (DB) flow. A comparison of the results indicates that the improved model using the NSWM flow can generally give results in better agreement with the test data and other published results than those by using NK and DB flows, especially for the hydrodynamic coefficients in relatively low frequency ranges

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

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

Ship manoeuvring model parameter identification using intelligent machine learning method and the beetle antennae search algorithm

In order to identify more accurately and efficiently the unknown parameters of a ship motions model, a novel Nonlinear Least Squares Support Vector Machine (NLSSVM) algorithm, whose penalty factor and Radial Basis Function (RBF) kernel parameters are optimised by the Beetle Antennae Search algorithm (BAS), is proposed and investigated Aiming at validating the accuracy and applicability of the proposed method, the method is employed to identify the linear and nonlinear parameters of the first-order nonlinear Nomoto model with training samples from numerical simulation and experimental data. Subsequently, the identified parameters are applied in predicting the ship motion. The predicted results illustrate that the new NLSSVM-BAS algorithm can be applied in identifying ship motion's model, and the effectiveness is verified. Compared among traditional identification approaches with the proposed method, the results display that the accuracy is improved. Moreover, the robust and stability of the NLSSVM-BAS are verified by adding noise in the training sample data

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

Alpha-tocopherol enhances spermatogonial stem cell proliferation and restores mouse spermatogenesis by up-regulating BMI1

PurposeSpermatogonial stem cells (SSCs) are essential for maintaining reproductive function in males. B-lymphoma Mo-MLV insertion region 1 (BMI1) is a vital transcription repressor that regulates cell proliferation and differentiation. However, little is known about the role of BMI1 in mediating the fate of mammalian SSCs and in male reproduction. This study investigated whether BMI1 is essential for male reproduction and the role of alpha-tocopherol (α-tocopherol), a protective agent for male fertility, as a modulator of BMI1 both in vitro and in vivo.MethodsMethyl thiazolyl tetrazolium (MTT) and 5-ethynyl-2′-deoxyuridine (EDU) assays were used to assess the effect of BMI1 on the proliferative ability of the mouse SSC line C18-4. Real-time polymerase chain reaction (PCR), western blotting, and immunofluorescence were applied to investigate changes in the mRNA and protein expression levels of BMI1. Male mice were used to investigate the effect of α-tocopherol and a BMI1 inhibitor on reproduction-associated functionality in vivo.ResultsAnalysis revealed that BMI1 was expressed at high levels in testicular tissues and spermatogonia in mice. The silencing of BMI1 inhibited the proliferation of SSCs and DNA synthesis and enhanced the levels of γ-H2AX. α-tocopherol enhanced the proliferation and DNA synthesis of C18-4 cells, and increased the levels of BMI1. Notably, α-tocopherol rescued the inhibition of cell proliferation and DNA damage in C18-4 cells caused by the silencing of BMI1. Furthermore, α-tocopherol restored sperm count (Ctrl vs. PTC-209, p = 0.0034; Ctrl vs. PTC-209 + α-tocopherol, p = 0.7293) and normalized sperm malformation such as broken heads, irregular heads, lost and curled tails in vivo, as demonstrated by its antagonism with the BMI1 inhibitor PTC-209.ConclusionAnalysis demonstrated that α-tocopherol is a potent in vitro and in vivo modulator of BMI1, a transcription factor that plays an important role in in SSC proliferation and spermatogenesis. Our findings identify a new target and strategy for treating male infertility that deserves further pre-clinical investigation

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