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All explicit immersed boundary–lattice Boltzmann (IB–LB) coupling schemes suffer from instability and restrictive choices of timestep and boundary rigidity. In this paper, an implicit IB–LB coupling method that can greatly alleviate those problems and easily incorporate the boundary mass is presented. The nonlinear equations resulting from the implicit discretization of the immersed boundary (IB) equations are solved by the Jacobian-free Newton–Krylov (JFNK) method, while the boundary mass is handled by introducing ghost boundaries. The improvement in stability is verified by two benchmark cases, and it is evident that both the maximal timestep and bending rigidity attained by the proposed implicit method can increase up to 200 times compared with those of the explicit version. The new method is applied to analyzing the vortex induced vibration of an impulsively started flexible filament, and both the simulated flow field and filament motion agree well with those obtained by particle image velocimetry (PIV). The influences of filament parameters on the vibration characteristics are discussed, and according to the results, the filament mass is the main influencing factor of vibration amplitude and the bending rigidity is the main influencing factor of vibration frequency.

This paper proposes an approach to accelerate the simulations of fluid structure interaction (FSI) by implementing the immersed boundary-lattice Boltzmann coupling scheme on a single GPU chip. For the lattice Boltzmann simulations, a standard procedure is adopted, in which the one-dimensional (1D) blocks and shared memory are used to solve the misalignment problems in global memory transactions. For the immersed boundary simulations, the sub-processes, including the velocity interpolation, boundary force computation and force spreading, are implemented by different kernels. Besides, the 1D arrays are used to store the information of all Lagrangian points, which can exploit the parallelism of Lagrangian points without violating the coalescing and aligned access pattern. The relaxation of a three-dimensional (3D) ellipsoidal membrane is simulated to assess the performance of the GPU implementation. All the GPU kernels are found to be bandwidth bound and the achieved memory efficiencies for LB, IB spreading and IB interpolation & forcing kernels are up to 66 % , 65 % and 61 % for a testing case. Finally, a strong FSI process of a 3D inflating and breaching balloon is simulated to demonstrate the capability of the present strategy.

Ethnopharmacological relevance Aconitum species, with a medicinal history of 2000 years, was traditionally used in the treatment of rheumatism, arthritis, bruises, and pains. However, many studies have reported that Aconitum species can cause arrhythmia in experimental animals, resulting in myocardial fibrosis and cardiomyocyte damage. Cardiotoxicity is the main toxic effect of aconitine, but the detailed mechanism remains unclear. Aim of the study This study aimed to explore the effects and underlying mechanism of autophagy in H9c2 cardiomyocytes induced by aconitine. Materials and methods H9c2 cells were incubated with different concentrations of aconitine for 24 h, and the intervention sections were pretreated with various inhibitors for 1 h. The effects of aconitine on the oxidative DNA damage, autophagy and viability of H9c2 cells were evaluated by flow cytometry, confocal microscopy, enzyme-linked immunosorbent assay and Western blot. Results In H9c2 cells, the cell viability declined, LDH release rate, the number of autophagosomes, protein expression levels of LC3 and Beclin-1 increased significantly after 24 h of aconitine incubation. The pretreatment of autophagy inhibitor 3-MA decreased markedly autophagosomes and protein expression levels of LC3 and Beclin-1, which suggested that aconitine could induce cell autophagy. The significant increase of ROS and 8-OHdG showed that aconitine could cause oxidative DNA damage through ROS accumulation. Meanwhile, treatment of aconitine dramatically increased AMPKThr172 and ULK1Ser317 phosphorylation, and Compound C inhibited AMPKThr172 and ULK1Ser317 phosphorylation, which proved that aconitine induced autophagy via AMPK activation mediated ULK1 phosphorylation. Antioxidant NAC significantly reduced LDH, ROS and 8-OHdG, inhibited the phosphorylation of AMPKThr172 and ULK1Ser317, and down-regulated autophagosomes and proteins expression levels of LC3 and Beclin-1. Consequently, the inhibition of oxidative DNA damage and AMPK/ULK1 signaling pathway alleviated the aconitine-induced autophagic death of H9c2 cells. Conclusions These results showed that aconitine induces autophagy of H9c2 cardiomyocytes by activating AMPK/ULK1 signaling pathway mediated by oxidative DNA damage. The autophagy induced by aconitine in cardiomyocytes is dependent on the activation of the AMPK pathway, which may provide novel insights into the prevention of aconitine-related toxicity.

Temperature jump at the boundary occurs when the conventional immersed boundary-lattice Boltzmann (IB-LB) method is applied to simulating the near boundary flows with heat transfer. To remedy this problem, an iterative correction is proposed to modify the heat source term in the IB-LB method. The source term in the LB equation is treated by Cheng’s scheme, in which the heat source at the next timestep is taken as unknowns and iteratively corrected until the resulting boundary temperature matches its desired value. Typical verification cases, including the two-dimensional (2D) heat transfer between two horizontal plates, the natural convection between two concentric circular cylinders, and 2D sedimentation of a single particle with heat convection are simulated to analyze the accuracy of the method. It is shown that the boundary temperature jump can be effectively removed for a certain range of LB relaxation time τ , while the first-order spatial convergence of the IB method is still maintained. Also, a theoretical analysis is conducted based on the case of heat transfer between two plates. It is shown that the proposed method outperforms the widely-used direct source method in treating the Dirichlet boundary conditions when τ is smaller than 1.624. To further demonstrate its capability for resolving complicated fluid-structure interaction problems, a three-dimensional sedimentation of a single particle in a vertical channel is analyzed. We find that the thermal convection may fundamentally affect the way the particle interacts with the surrounding fluid.

The problem of impaired data sets refers to data sets containing a vast majority of unwanted signals than signals of interest. With increased interest in partial discharge (PD) testing with arbitrary waveforms and transients, these kind of data sets are becoming more and more common. Traditional clustering techniques cannot be applied due to big differences in spatial densities of the existing clusters in the data set. This paper contributes a simple yet efficient technique to recognize PD signals from noise and other disturbances. The signal recognition features are based on two specific areas extracted from the cumulative energy signal (CE) of each recorded waveform. These areas weigh up the extent to which the recorded signals have a pulse-like shape. A third feature, defined as a shape factor, extracts additional metrics from the CE signal that serves the purpose of accounting for the factors affecting the computation of the proposed recognition features and threshold for data size reduction. These three CE-based features are used to create a graph from which a real PD can be spotted in large impaired data sets. The performance of this technique is tested using PD measurements from superimposed impulse tests on a 150 kV cable system.

We present our recent progress on microwave signal processing (MSP) using on-chip passive silicon photonic devices, including tunable microwave notch filtering/millimeter-wave (MMW) signal generation based on self-coupled micro-resonators (SCMRs), and tunable radio-frequency (RF) phase shifting implemented by a micro-disk resonator (MDR). These schemes can provide improved flexibility and performances of MSP. The experimental results are in good agreement with theoretical predictions, which validate the effectiveness of the proposed schemes.

The non-slip boundary condition at solid walls cannot be accurately achieved by the conventional immersed boundary–lattice Boltzmann (IB–LB) coupling schemes due to insufficient interpolation accuracy. To solve this problem, an iterative force correction procedure for the IB–LB coupling scheme is proposed. Cheng’s external forcing term in the LB equation is selected to properly incorporate the present and the next time step effects. The unknown IB force and the corresponding force on fluid at the next time step are calculated by iterative correction, based on the known immersed boundary speed, flow velocity, and the relationship between the IB speed and the IB force. Instead of the Dirac delta function, the Lagrange interpolation polynomial is used to obtain the IB speed from nearby fluid velocity. Typical cases, including the flow around a circular cylinder, shearing flow near a non-slip wall, and circular Couette flow between two inversely rotating cylinders, are simulated to verify and validate the method. It is shown that the present method guarantees the non-slip boundary condition and maintain the overall first-order spatial convergence rate of the conventional immersed boundary method (IBM). The accuracy improvement is obvious for both stationary and moving solid boundaries in both viscous flows and strong shearing flows. To demonstrate application possibility, a mechanical heart valve flow is also simulated, and better agreements with experimental data are achieved compared to those by commercial software.

An integrated system combined direct air capture (DAC) and greenhouse agriculture is proposed, in which moisture swing adsorption technology is used to concentrate CO 2 from the atmosphere and then feed CO 2 to the greenhouse. Absorption isotherm study and desorption kinetic study have been achieved in the paper. The results show that the behaviour of membrane conforms to Langmuir model and its capacity reaches to 0.83 mol of CO 2 per kilogram of sorbent. When the output CO 2 concentration of the desorber is around 1000 ppm, desorption efficiency increases from 71.3% to 79.6% when the temperature is changed from 25 °C to 40 °C. Besides, based on the experiment of the uptake kinetics of plants under different light and different light intensity, energy consumption and techno-economic analysis of the system have been carried out.

We propose a compact silicon-based modulator for 16-point quadrature amplitude modulation (16-QAM) with a simple structure using two phase shifters. The phase shifters employ low-loss hybrid plasmon waveguide, consisting of a conductor-gap-dielectric structure filled with polymer. Combining the strong optical confinement ability of the plasmonic waveguide with the highly nonlinear characteristic of the polymer, the proposed 16-QAM modulator can achieve a compact footprint, high-speed operation, and low power consumption, potentially allowing for high-density on-chip integration and broadband long-haul optical transmission.