A hybrid stabilization technique for simulating water wave - Structure interaction by incompressible Smoothed Particle Hydrodynamics (ISPH) method

The Smoothed Particle Hydrodynamics (SPH) method is emerging as a potential tool for studying water wave related problems, especially for violent free surface flow and large deformation problems. The incompressible SPH (ISPH) computations have been found not to be able to maintain the stability in certain situations and there exist some spurious oscillations in the pressure time history, which is similar to the weakly compressible SPH (WCSPH). One main cause of this problem is related to the non-uniform and clustered distribution of the moving particles. In order to improve the model performance, the paper proposed an efficient hybrid numerical technique aiming to correct the ill particle distributions. The correction approach is realized through the combination of particle shifting and pressure gradient improvement. The advantages of the proposed hybrid technique in improving ISPH calculations are demonstrated through several applications that include solitary wave impact on a slope or overtopping a seawall, and regular wave slamming on the subface of open-piled structure

Magnetic control of the pair creation in spatially localized supercritical fields

We examine the impact of a perpendicular magnetic field on the creation mechanism of electron-positron pairs in a supercritical static electric field, where both fields are localized along the direction of the electric field. In the case where the spatial extent of the magnetic field exceeds that of the electric field, quantum field theoretical simulations based on the Dirac equation predict a suppression of pair creation even if the electric field is supercritical. Furthermore, an arbitrarily small magnetic field outside the interaction zone can bring the creation process even to a complete halt, if it is sufficiently extended. The mechanism for this magnetically induced complete shutoff can be associated with a reopening of the mass gap and the emergence of electrically dressed Landau levels

High-Speed, Heavy-Load, and Direction-Controllable Photothermal Pneumatic Floating Robot.

Light-fueled actuators are promising in many fields due to their contactless, easily controllable, and eco-efficiency features. However, their application in liquid environments is complicated by the existing challenges of rapid deformation in liquids, light absorption of the liquid media, and environmental contamination. Here, we design a photothermal pneumatic floating robot (PPFR) using a boat-paddle structure. Light energy is converted into thermal energy of air by an isolated photothermal composite, which is then converted into mechanical energy of liquid to drive the movement of PPFRs. By understanding and controlling the photothermal actuation, the PPFR can achieve an average velocity of 13.1 mm s-1 in water and can be modified for remote on-demand differential steering and self-sustained oscillation. The PPFR may be modified to provide a lifting mechanism, capable of moving 4 times the PPFR mass. Various shapes and materials are suitable for the PPFR, providing a platform for liquid surface transporting, water sampling, pollutant collecting, underwater photography, and photocontrol robots in shallow water

An improved solid boundary treatment for wave-float interactions using ISPH method

The Smoothed Particle Hydrodynamics (SPH) method has proved to have great potentials in dealing with the wave-structure interactions. Compared with the Weakly Compressible SPH (WCSPH) method, the ISPH approach solves the pressure by using the pressure Poisson equation rather than the equation of state. This could provide a more stable and accurate pressure field that is important in the study of wave-structure interactions. This paper improves the solid boundary treatment of ISPH by using a high accuracy Simplified Finite Difference Interpolation (SFDI) scheme for the 2D wave-structure coupling problems, especially for free-moving structure. The proposed method is referred as the ISPH_BS. The model improvement is demonstrated by the documented benchmark tests and laboratory experiment covering various wave-structure interaction applications

Diversity of eukaryotic plankton of aquaculture ponds with Carassius auratus gibelio, using denaturing gradient gel electrophoresis

PCR-denaturing gradient gel electrophoresis (DGGE) and canonical correspondence analysis (CCA) were used to explore the relationship between eukaryotic plankton community succession and environmental factors in two aquaculture pond models with gibel carp Carassius auratus gibelio. The main culture species of pond 1 were gibel carp and grass carp, and the combined density was 46224 fingerling/ha (gibel carp/grass carp/silver carp/bighead carp, 17:4:6:1). The main culture species of pond 2 was gibel carp, and the combined density was 37551 fingerling/ha (gibel carp/silver carp/bighead carp, 52:1:1). Water samples were collected monthly. The results showed that the annual average concentrations of TP and PO_4-P in pond 1 were significantly higher than pond 2 (p>0.05). The concentration of chlorophyll a (chl a) has no significantly difference between pond 1 and pond 2. DGGE profiles of 18S rRNA gene fragments from the two ponds revealed that the diversity of eukaryotic plankton assemblages was highly variable. 91 bands and 71 bands were detected in pond 1 and pond 2, respectively. The average Shannon–Wiener index of pond 1 was significantly higher than pond 2. Canonical correspondence analysis (CCA) revealed that temperature played a key role in the structure of the eukaryotic plankton community in both ponds, but the nutrient concentration did not affect it. Our results suggest that DGGE method is a cost-effective way to gain insight into seasonal dynamics of eukaryotic plankton communities in culture ponds, and the increase in the number of filter-feeding silver carp and bighead carp could increase the diversity of the eukaryotic plankton community

Antiviral treatment alters the frequency of activating and inhibitory receptor-expressing natural killer cells in chronic Hepatitis B virus infected patients

Natural killer (NK) cells play a critical role in innate antiviral immunity, but little is known about the impact of antiviral therapy on the frequency of NK cell subsets. To this aim, we performed this longitudinal study to examine the dynamic changes of the frequency of different subsets of NK cells in CHB patients after initiation of tenofovir or adefovir therapy. We found that NK cell numbers and subset distribution differ between CHB patients and normal subjects; furthermore, the association was found between ALT level and CD158b+ NK cell in HBV patients. In tenofovir group, the frequency of NK cells increased during the treatment accompanied by downregulated expression of NKG2A and KIR2DL3. In adefovir group, NK cell numbers did not differ during the treatment, but also accompanied by downregulated expression of NKG2A and KIR2DL3. Our results demonstrate that treatment with tenofovir leads to viral load reduction, and correlated with NK cell frequencies in peripheral blood of chronic hepatitis B virus infection. In addition, treatments with both tenofovir and adefovir in chronic HBV infected patients induce a decrease of the frequency of inhibitory receptor+ NK cells, which may account for the partial restoration of the function of NK cells in peripheral blood following treatment

Forecasting China's wastewater discharge using dynamic factors and mixed-frequency data

Forecasting wastewater discharge is the basis for wastewater treatment and policy formulation. This paper proposes a novel mixed-data sampling regression model, i.e., combination-MIDAS model to forecast quarterly wastewater emissions in China based on dynamic factors at different frequencies. The results show that a significant auto-correlation for wastewater emissions exists and that water consumption per ten thousand gross domestic product is the best predictor of wastewater emissions. The forecast performances of the combination-MIDAS models are robust and better than those of the benchmark models. Therefore, the combination-MIDAS models can better capture the characteristics of wastewater emissions, suggesting that the proposed method is a good method to deal with model misspecification and uncertainty for the control and management of wastewater discharge in China. (C) 2019 Elsevier Ltd. All rights reserved

The implement of plastic oval tags for mark-recapture in juvenile Japanese flounder (Paralichthys olivaceus) on the northeast coast of Shandong Province, China

As part of the stock enhancement research project of Shandong Province, China, plastic oval tags (POTs) were used to mark juvenile Japanese flounder for release, Paralichthys olivaceus (70 to 133 mm total length, TL), in 2009 and 2010. Optimal tag placement locations, retention, tagging rates, and mortality were initially evaluated. Mark–recapture experiments were carried out in the coastal waters of Weihai City to study their migratory movements: 21,202 individuals in July 2009 at Beihai and 18,350 individuals in July 2010 at Lidao. The number of recaptured individuals were 434 (2.05% recapture rate) in 2009 and 620 (3.38% recapture rate) in 2010. A radiative movement from the release site was observed in the 2009 experiment; however, the tagging experiment showed a predominantly northward dispersal of tagged flounder from the release site in 2010. The mean movement speed of the released fish was calculated as 0.46 km day-1 in 2009 and 1.05 km day-1 in 2010. Furthermore, in 2009, the average TL and wet mass increments were 36.3 ± 8.4 mm month-1 and 27.13 ± 16.09 g month-1, respectively 1 to 6 months after releasing; however, the increments were 14.7 ± 8.8 mm month-1 and 5.65 ± 4.17 g month-1, respectively in 2010.Key words: Paralichthys olivaceus, plastic oval tag, mark–recapture, movement, growth