Arsenic (As), a well-known ‘traditional’ environmental contaminant, and carbamazepine (CBZ), an emerging contaminant of a pharmaceutical category, are both frequently detected in the environment and have been shown to exhibit toxicity at exposure concentrations present in the environment. This study aimed to assess the single and combined exposure effects of these pollutants on the adult common vole (Microtus arvalis L.), a model mammalian organism. This study assessed As and CBZ accumulation, their biotransformation processes, and antioxidant enzyme defence responses after sole and combined exposure. The animals were fed a diet containing either a low (1.25 mg/kg) or high level (166 mg/kg) of As. Moreover, half of the animals were exposed to CBZ via drinking water infused with 10 ng/L of CBZ, and the second half had the use of drinking water devoid of CBZ. The results showed enhanced total As and As species contents in the organs of the As + CBZ exposure group compared to the As exposure group. High As exposure in the As + CBZ group did not cause an enhanced uptake of CBZ in the liver compared to the CBZ exposure group. There was a potential accumulation of CBZ in the liver of the CBZ exposed groups (CBZ and As + CBZ), raising concerns about potential toxic effects in mammals from long-term exposure. Glutathione peroxidase (GPx) activity, reflecting the antioxidant enzyme defence responses against single and co-exposure of the two pollutants, showed that the CBZ group exhibited comparable activity to the control group, while the As group had down-regulation and the As + CBZ group had up-regulation. These findings suggest that the CBZ group experienced minimal oxidative stress conditions, similar to the control group. The As group showed a rapid adaptation response to curtail or offset potential oxidative stress tissue damage conditions, compared to the slow adaptation/response in the As + CBZ group. The findings of this experiment indicate that the possible interactions of various environmental pollutants could alter the potential effects of the individual pollutants after a sole exposure. These findings indicate the necessity of investigating these interactions for better understanding of the potential risk of these pollutants in real environmental conditions.
Reactive powder concrete (RPC) is widely used in ultra-high-rise buildings, hydropower stations, bridges, and other important infrastructures. To study the dynamic response and damage characteristics of RPC columns and frames considering coupled fire and explosions, an analytical model of RPC columns and frames with coupled fire and explosions was established by using ABAQUS (2021) finite element software. The dynamic response and damage degree of RPC columns under coupled fire and explosions were investigated to reveal the influence laws of parameters such as cross-section size, axial compression ratio, reinforcement rate, and fire duration on the dynamic response of RPC columns at high temperatures. The dynamic response of the frame structure was analyzed when the explosion load was applied to the bottom corner columns, side columns, and top beams, respectively. The results show that the fire severely weakened the blast resistance of RPC columns; the maximum mid-span deformation and residual deformation of RPC columns decreased with the increase in cross-section size and longitudinal bar reinforcement ratio and increased with the increase in fire duration and axial compression ratio. When the explosion load was applied to the corner columns of the bottom floor of the frame, the bottom corner columns were almost completely destroyed, and there was a significant risk of the structure collapsing. Based on the results of the data analysis, a method to enhance the explosion resistance of RC frame structures using RPC materials at high temperatures is proposed.
This study aims to examine the spatiotemporal variations of extreme rainfall events in Seoul, South Korea, utilizing subhourly rainfall data collected from an extensive observation network. Employing the Mann–Kendall trend detection test and Moran’s I index, this study analyzed temporal trends and spatial distributions in the extreme rainfall time series at 37 weather stations. The findings revealed that the annual maximum precipitation (AMP) series for various durations in Seoul generally exhibited a decreasing trend, with a marked decline observed for durations of 300 and 360 min. Furthermore, the study identified notable changes in the spatial patterns of AMP events, particularly for subhourly AMP events. The results indicate an intensification in the spatial concentration of AMP distribution. Consequently, despite the overall reduction in AMP, the likelihood of urban flooding may increase. This suggests that existing hydraulic design criteria, based on past concepts that temporal and spatial variability are constant, may no longer adequately represent extreme rainfall events. Therefore, revising these criteria to account for the evolving nature of extreme rainfall patterns is imperative.
The method proposed in this paper provides a new research idea for biomimetic three-dimensional grid structure material design. The wings of a dragonfly exhibit a complex grid structure, comprising approximately 1–2% of its total weight, yet demonstrating exceptional mechanical efficiency. In order to investigate the feasibility of applying the design optimization method simulating this structure to the material structure design, we adopted a multi-step method to realize the formation of multi-scale grid structures and folds. Initially, the main vein of the front wing was simulated using a branching structure generation technique. Subsequently, a Voronoi grid was overlaid to generate the complete bionic grid structure. Finally, the fold structure of the wing was simulated using origami principles to create a three-dimensional grid structure. This method can obtain the rigid–flexible coupling 3D grid structure by simulating the 3D fold structure design of the dragonfly wing. The results show that the proposed method can obtain structural materials with excellent structural properties by simulating the structural characteristics of dragonfly wings.
This research focuses on the dynamic analysis of an oscillating conveyor mechanism using numerical methods to solve nonlinear differential equations that govern its motion. The system under study is modeled by a second-order differential equation of the form R(t)dω1dt+Q(t)ω12(t)=W(t), where R(t), Q(t), and W(t) are time-dependent functions representing system parameters such as resistance, damping, and external driving forces. To solve these equations, we employed a numerical approach based on Euler’s method, which discretizes the time domain into small steps h and approximates the derivatives of angular velocity and angular displacement. The angular velocity ωk+1 and angular displacement φk+1 are updated iteratively using the formulas ωk+1=ωk+h(WkRk−QkRkωk2) and φk+1=φk+hωk, respectively. Initial conditions, with ω0=0 and φ0=0, were specified, and the system was simulated over a specified time range divided into N time steps. In the simulation, key parameters such as A(t), B(t), D(t), E(t), F(t), H(t), N(t), M(t), Q(t), R(t), and W(t) were evaluated at each time step based on the system’s geometry and the angular displacements. Due to the complexity of the system, analytical solutions were impractical, so the Runge–Kutta method was employed for higher accuracy in the integration process. The results from the numerical simulations were validated by comparing them with theoretical expectations, and the system’s dynamic behavior was visualized using time-series and 3D plots. The simulation demonstrated that the system’s stability and accuracy were highly dependent on the time step h, with smaller values providing more precise results at the cost of increased computational time. The research confirms the applicability of numerical methods in solving complex nonlinear differential equations for dynamic systems and provides insights into the system’s behavior under various operating conditions.
