Predictors of Permanent Pacemaker Implantation in Patients After Transcatheter Aortic Valve Replacement in a Chinese Population

Background: Permanent pacemaker (PPM) implantation is the main complication of transcatheter aortic valve replacement (TAVR). Few studies have evaluated the requirement for PPM implantation due to ECG changes following TAVR in a Chinese population.Objective: Our study aimed to evaluate the incidence and predictors of PPM implantation in a cohort of Chinese patients with TAVR.Methods: We retrospectively evaluated 39 consecutive patients with severe native aortic stenosis referred for TAVR with a self-expandable prosthesis, the Venus A valve (Venus MedTech Inc., Hangzhou, China), from 2019 to 2021 at the Heart Center of Affiliated Zhongshan Hospital of Dalian University. Predictors of PPM implantation were identified using logistic regression.Results: In our study, the incidence of PPM implantation was 20.5%. PPM implantation occurs with higher risk in patients with negative creatinine clearance (CrCl), dyslipidemia, high Society of Thoracic Surgeons (STS) Morbimortality scores, and lead I T wave elevation. TAVR induced several cardiac electrical changes such as increased R wave and T wave changes in lead V5. The main independent predictors of PPM implantation were new-onset left bundle branch block (LBBB) (coef: 3.211, 95% CI: 0.899–7.467, p = 0.004) and lead I T wave elevation (coef: 11.081, 95% CI: 1.632–28.083, p = 0.016).Conclusion: New-onset LBBB and lead I T wave elevation were the main independent predictors of PPM implantation in patients undergoing TAVR. Clinical indications such as negative CrCl, dyslipidemia, high STS Morbimortality scores, and an increased T wave elevation before TAVR should be treated with caution to decrease the need for subsequent PPM implantation.

Power Enhancement of WEC Array via Wave Runup in Channel

When waves pass through a channel, wave elevation is observed to increase, a phenomenon known as wave runup. Attempts are made to utilize the wave runup along a channel supported on a floating platform to enhance the energy generation from the array of point absorber WECs. Such floating platforms could be integrated into the floating breakwater, floating pier or other floating platforms utilized as floating cities for efficient ocean space utilization. The channel is created by modelling two vertical walls supported on a floating platform with WECs deployed in the channel. The performance of the wave farm in terms of energy generation and interaction factor are assessed. The paper investigates the effect of channel widths and depths on the power absorption of the arrays. A three-stepped floating platform with varying depths along the channel is then studied to obtain optimal depths along the channel where the highest energy is harvested. Thereafter, three arrays of WECs deployed in a larger three-stepped channel floating platform are considered and the effectiveness of such configuration in harvesting energy is assessed. The wave elevation surrounding the wave farm is presented to show the effect the wave runup has on energy generation. The results show that the energy generation of wave energy converters when the arrays are placed in a three-stepped channel floating platform could be increased significantly. A q-factor above 1.0 could be achieved for wave periods greater than 6s and the array can generate greater energy for omnidirectional waves.

STUDY OF FROUDE AND HUGHES METHODS BY NUMERICAL TOWING TANK

The resistance of a cargo ship is calculated by numerical towing tank. RANSE multi-phase parallel solver with K-Z SSTturbulent model and VOF formulation is applied. Computational results from double model (without free surface) areused to obtain 1+k in Hughes’ method and those with free surface are analyzed by both Froude and Hughes’ approachesto investigate model and full scale correlation. ITTC recommended uncertainty study is carried out to evaluate numericalerror due to grid density. The computed wave elevation, wake distribution and resistance components by fine, mediumand coarse meshes are cross-compared and validated against experiment data where applicable. It is found that gridresolution has most effect on wave pattern. The predicted friction and viscous-pressure resistance coefficients arerelatively grid independent from present numerical simulation.

Wave Elevation for an Array of Columns Under Wave-Current Interactions

A wave and current diffraction model is developed based on the potential flow theory and a high-order boundary element method with the successful treatment of singular and nearly singular integrals. The wave-current diffraction from four mounted cylindrical columns are computed, and the free surface wave elevations among the columns are investigated. The influences of the current speed, wave direction, and column spacing on the wave elevation are examined. Ultimately, the presence of a current has a significant influence on the magnitude, spatial location and occurrence frequency of the maximum wave elevation.

Sea Spectral Estimation Using ARMA Models

This paper deals with the spectral estimation of sea wave elevation time series by means of ARMA models. To start, the procedure to estimate the ARMA coefficients, based on the use of the Prony’s method applied to the auto-covariance series, is presented. Afterwards, an analysis on how the parameters involved in the ARMA reconstruction procedure—for example, the signal time length, the number of poles and data used—affect the spectral estimates is carried out, providing evidence on their effect on the accuracy of results. This allowed us to provide guidelines on how to set these parameters in order to make the ARMA model as accurate as possible. The paper focuses on mono-modal sea states. Nevertheless, examples also related to bi-modal sea states are discussed.

The Harmonic Structure of the Focused Wave in a Wave Flume

In recent years, extreme waves have attracted more and more attention due to its threat to offshore and coastal structures. It is essential to obtain further insight into the formation and propagation of the extreme waves. The formation of extreme waves mainly comes from the simultaneous focusing of wave group energy in the ocean. In the present study, the nonlinear characteristics of the extreme wave are experimentally investigated by the wave focusing method. The phase decomposition methods, both two-phases separation and four-phases separation methods, are used to obtain the higher harmonic elevation in the focused wave. The results show that the four-phases separation method can reasonably extract the first four harmonics. With the separated results, the nonlinear analysis of the wave elevation and velocity of the focused wave is carried out. It is found that the harmonics of the wave group focused at the same time, but the wave elevation and energy of higher-order harmonics are smaller than that of the overall wave. The Stokes wave theory can describe the variation of second-order harmonics satisfactorily. However, the Stokes wave theory cannot estimate third-order harmonics accurately. More work should be carried out to figure out the third-order wave interaction occurring during wave focusing. With a distributed wave gauge system, the wave evolution along the wave flume is measured. The evanescent modes significantly influence the wave group’s harmonic structure near the wavemaker. The coefficients of the higher-order harmonics are obtained from the measured elevations. The nonlinear wave elevation of the focused wave can be reconstructed with those coefficients basing on the linear theoretical solution, which is in good agreement with the experimental results.

Numerical Estimation of Relative Wave Elevation on a Semi-Submersible Vessel

Ambition of this research was to numerically reproduce the relative wave elevations measured on and around a semi-submersible vessel during model tests performed at MARIN (Maritime Research Institute of the Netherlands). Model tests were performed on a semi-submersible model representing, in different setup configurations, a heavy lift vessel and a LPD (Landing Platform Dock). Relative wave elevations were measured at 47 locations on and around the vessel. Tests were made with different regular wave conditions and headings, at anchor, with the model fixed in a soft mooring setup. Data from model tests were used to calibrate and run a time domain potential flow boundary element tool with particular focus on the relative wave elevation at the 47 locations. A comparison between numerical and experimental results is proposed in this paper.

Experimental and FNPT-RANS Investigations Into Gap-Excitation and Vortex Dynamics in a Rectangular Moonpool Interacting With Focused Waves

Moonpools are designed to provide a calm environment for lowering of equipment from ships. Considerable research effort has been invested towards understanding water column excitation within a moonpool. However, most recent investigations consider regular waves. The nature of interaction between focused waves and a moonpool is not well-understood; the present work strives to fill this research gap. A series of experiments have been carried out in a 22 m long glass flume in the Department of Ocean Engineering at IIT Madras. Two identical cuboidal boxes were affixed with a 0.15 m gap representing a rectangular moonpool. Focused waves based on a constant steepness spectrum were generated in 0.6 m water depth by a piston-type wave-paddle. The focusing point was set at the center of the moonpool and wave-focusing experiments were performed with and without the twin-body. Wave elevation at various locations along the flume was measured using five wave-gauges. Next, the experiments were numerically replicated using the in-house codes IITM-FNPT2D (for inviscid wave generation) and IITM-RANS3D (for fully viscous wave-structure interaction). Gap-excitation at the instant of focusing has been quantified and correlated with focused wave characteristics and with dynamics of spanwise vortices generated at the edges of the moonpool.