Predicting changes in molluscan spatial distributions in mangrove forests in response to sea-level rise

Molluscs are an important component of the mangrove ecosystem, and the vertical distributions of molluscan species in this ecosystem are primarily dictated by tidal inundation. Thus, sea-level rise (SLR) may have profound effects on mangrove mollusc communities. Here, we used two dynamic empirical models based on measurements of surface elevation change, sediment accretion and zonation patterns of molluscs to predict changes in molluscan spatial distributions in response to different sea-level rise rates in the mangrove forests of Zhenzhu Bay (Guangxi, China). The change in surface elevation was 4.76–9.61 mm a during the study period (2016–2020), and the magnitude of surface-elevation change decreased exponentially as original surface elevation increased. Based on our model results, we predicted that mangrove molluscs might successfully adapt to a low rate of SLR (marker-horizon model: 2–4.57 mm a; plate model: 2–5.20 mm a) by 2100, with molluscs moving seaward and those in the lower intertidal zones expanding into newly available zones. However, as SLR rate increased (marker-horizon model: 4.57–8.14 mm a; plate model: 5.20–6.88 mm a), our models predicted that surface elevations would decrease beginning in the high intertidal zones and gradually spreading to the low intertidal zones. Finally, at high rates of SLR (marker-horizon model: 8.14–16.00 mm a; plate model: 6.88–16.00 mm a), surface elevations were predicted to decrease across the elevation gradient, with molluscs moving landward and species in higher intertidal zones would be blocked by landward barriers. Tidal inundation and the consequent increase in interspecific competition and predation pressure were predicted to threaten the survival of many molluscan groups in higher intertidal zones, especially species at the landward edge of the mangroves. Thus, future efforts to conserve mangrove floral and faunal diversity should prioritize species restricted to landward mangrove areas.

Nonlinear thermal vibration of a nanoplate attached to a cavity

Dynamic problems of a nanocircular plate-cavity system are investigated using molecular dynamics (MD) method. A nonlinear plate model considering gas action is developed. The results of the MD simulation show that the helium atoms adsorb on the wall of the cavity at low temperature, resulting in a negative deflection of the molybdenum disulfide (MoS2) plate. As the temperature increases, the pressure in the cavity increases, leading to a gradual rise in the deflection of the plate. A nonlinear phenomenon of stiffness hardening is shown with increasing temperature. The nonlinear plate model can give a relatively good prediction compared with the results of MD simulations. The natural frequency of the plate is affected by temperature and the presence of gas in the cavity. The phenomenon of stiffness hardening and softening can be well simulated by the nonlinear plate model and MD method. The present study provides a reference for vibration experiments of two-dimensional nanostructures.

Nonlinear Finite Element Analysis of Free and Forced Vibrations of Cellular Plates Having Triangularly Prismatic Metamaterial Cores: A Strain Gradient Plate Model Approach

The main objective of this paper is to develop a theoretically and numerically reliable and efficient methodology based on combining a finite element method and a strain gradient shear deformation plate model accounting for the nonlinear free and forced vibrations of cellular plates having equitriangularly prismatic metamaterial cores. The proposed model based on the nonlinear finite element strain gradient elasticity is developed for the first time to provide a computationally efficient framework for the simulation of the underlying nonlinear dynamics of cellular plates with advanced microarchitectures. The corresponding governing equations follow Mindlin’s SG elasticity theory including the micro-inertia effect applied to the first-order shear deformation plate theory along with the nonlinear von Kármán kinematics. Standard and higher-order computational homogenization methods determine the classical and strain gradient material constants, respectively. A higher-order \({C}^{1}\)-continuous 6-node finite element is adopted for the discretization of the governing variational formulation with respect to the spatial domain, and an arc-length continuation technique along with time periodic discretization is implemented to solve the resulting nonlinear time-dependent problem. Through a set of comparative studies with 3D full-field models as references, the accuracy and efficacy of the proposed dimension reduction methodology are demonstrated for a diverse range of problem parameters for analyzing the large-amplitude dynamic structural response.

Evolution of artificial disturbances in a shear layer at M=1.43

The evolution of artificial disturbances in a laminar boundary layer on a flat plate model in the presence of an incident shock wave is considered. The flow is supersonic with the freestream Mach number M = 1.43. The study is carried out by hot-wire anemometry. A dielectric barrier discharge is used to generate disturbances. Data on the distribution in space of the average and non-stationary components of the mass flow are obtained. Disturbances created by the discharge and their evolution along the separation zone are recorded.