Search Results (4,138)

The extensive use of 2,4-dichlorophenoxyacetic acid (2,4-D) in agriculture has led to water contamination and associated health risks, highlighting the need for eco-friendly detection strategies. Herein, Fe₃O₄ nanoparticles were green-synthesized for the first time using an aqueous extract of Rumex nervosus (R. nervosus) as a natural reducing and stabilizing agent and successfully employed for the electrochemical sensing of 2,4-D, representing the first reported application of R. nervosus-mediated Fe₃O₄ nanoparticles for this purpose. The phytochemical composition of the extract and synthesized R-Fe₃O₄ nanoparticles were systematically characterized. The R-Fe₃O₄-modified glassy carbon electrode (GCE) was evaluated for charge transfer properties using electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) showed no redox peak for 2,4-D at the bare GCE, whereas R-Fe₃O₄/GCE exhibited a distinct reduction peak at ~−1.5 V in 0.1 M phosphate buffer (pH 7), attributed to reductive dechlorination. Square-wave voltammetry (SWV) exhibited a linear response over the concentration range of 50–325 µM with a detection limit of 3.35 µM for 2,4-D. Although this performance is slightly above the guideline limits recommended by the World Health Organization (~0.14 µM) and the United States Environmental Protection Agency (~0.32 µM), it is suitable for the routine monitoring of elevated 2,4-D levels in environmental samples. The sensor demonstrated high selectivity with negligible interference and satisfactory recoveries of 96.6–98.3% in real water samples. Full article

A study was conducted on the interaction of surface gravity waves with a relatively thin, free-floating ice floe compared to the height of the waves. Physical and numerical modeling, as well as analytical research, were used. An overview of scientific works on the research topic is presented. The physical model consisted of an experimental setup (wave flume) with a wooden plate exposed to gravitational harmonic waves of different lengths and periods. The numerical model is based on calculations performed in the LS-DYNA program, where the fluid was simulated using the Euler–Lagrange method, and solid bodies were considered rigid. Analytical studies use the theory of interaction of small-amplitude waves with floating breakwaters. It is shown that as the wave height increases for conditions of interaction between waves and ice floes of almost identical horizontal dimensions, one end of the floating body sinks into the water, which leads to a significant reduction in the drift speed of the ice floe. Formulas have been obtained that express the ratio of the ice floe’s speed to the wave velocity, as well as the ratio of the height of the incident waves to the height of the transmitted waves, depending on the ratio of the wavelength to the horizontal dimensions of the floating ice floe. Full article

Freak waves can cause damage or capsize marine structures. The efficient fixed-point generation of target wave trains containing freak waves in laboratories or numerical wave tanks is a crucial method for marine structure design and disaster inversion assessment. This study proposes a local coefficient assignment method. After no more than three iterations of local wave train processing, the method achieves accurate generation of measured freak wave trains at different positions. Among the results, the maximum crest error for the “New Year Wave” is less than 3%, and the simulation achieves excellent agreement in significant wave height, period, and overall wave surface elevation with the target wave surface. The assignment coefficient curve of the typical freak wave event “New Year Wave” within the farthest fixed-point generation range of the numerical simulation in this paper is provided, enabling high-precision one-time generation of the “New Year Wave” at any desired position. The resulting maximum wave height error is less than 5%, satisfying the application requirements of deep-water waves under different water depth conditions. Furthermore, based on the simulation results, wavelet transform analysis is performed on the wave train data to investigate the evolution characteristics of wave energy before, during, and after the occurrence of the freak wave. The findings of this study have strong practical engineering significance for research on the propagation and evolution characteristics of highly nonlinear waves, as well as for the design and analysis of wave loads on marine structures. Full article

Supercritical CO₂ gas explosion is an important technique for enhancing permeability in low-permeability coal seams, as it can improve gas drainage efficiency while avoiding the open-flame hazards of conventional explosion and the high water consumption associated with hydraulic fracturing. This study aims to reveal the crack propagation patterns and stress-wave dynamics under different hole configurations. Using LS-DYNA, fracture models were established for three configurations under supercritical CO₂ explosions: single-hole, symmetrical double-hole, and symmetrical double-hole with a control hole. The fracture processes were analyzed to investigate the effective fracture radius of single-hole explosions, the optimal spacing for symmetrical double-hole explosions, and the influence of control holes on crack development and connectivity. The simulation results indicate that the effective fracture radius of a single-hole explosion reaches up to 2.6 m under the modeled conditions. Compared with the single-hole gas explosion case, the symmetrical double-hole configuration with a spacing of 7 m significantly enhances fracture interaction and connectivity, resulting in an approximately 98% increase in the effective damaged area. Permeability enhancement was further quantified by introducing a damage–permeability mapping (k/k₀) based on the simulated damage factor, and the permeability-enhanced zone was evaluated using the criterion of k/k₀ ≥ 2. Full article

This paper presents a theoretical analysis of frequency shifts in broadband acoustic field interference structures caused by an internal soliton wave in shallow water. It analyzes the spectral signature of interference-maxima frequency shifts within a coupled-mode framework that describes the scattering of acoustic normal modes under soliton-induced perturbations. Using the weak coupling approximation, analytical expressions are obtained for modal phase variations and the spectral peak frequency associated with the temporal evolution of frequency shifts induced by internal soliton waves. The analytical estimates obtained in the weak coupling approximation are extensively validated using numerical simulations under realistic ocean conditions without invoking it. This paper’s theoretical analysis demonstrates that internal soliton wave-induced mode coupling produces frequency shift spectrum signatures that strongly depend on soliton parameters. These results suggest that it is potentially feasible to estimate key soliton parameters, such as propagation direction, velocity, and effective amplitude, from measured frequency shifts. Numerical simulations demonstrate the feasibility of solving this inverse problem. These findings highlight the potential of frequency shift analysis as a practical, robust tool for remote sensing of internal wave dynamics in ocean acoustics. Full article

The thermal conductivity (λ) of porous rocks as a function of total porosity, grain size, and fluid saturation is measured and modeled by combining high-precision experiments with a Staged Differential Effective Medium (SDEM) modeling framework. A 1-D divided-bar apparatus with computer-controlled guard heaters with an integrated ultrasonic pulse-transmission system was developed to measure the thermal conductivity and P and S-wave velocities simultaneously. Measurements were made on Fontainebleau sandstone cores and quartz sand packs of varying grain size and effective stresses up to 2000 psi. The sample properties were measured in both dry and water-saturated states. The SDEM model performs significantly better at predicting the saturated thermal conductivities in the sand packs. For the sand packs, the thermal conductivity and compressional velocity are the highest and most stress-sensitive for the fine-grained material. In contrast, the shear velocity is largest in the coarse-grained material. The SDEM model is adapted from previous acoustic models for use in understanding thermal conductivity. These joint models accurately reproduce the evolution of both thermal conductivity and bulk modulus during increasing compaction and varying saturation. A single parameter fits both the dry and saturated data, which allows Gassmann-style fluid substitution for the thermal conductivity. This model improves the prediction of in situ thermal conductivity from sonic well logs. Full article

Ras El-Bar, a premier historic coastal resort on Egypt’s Nile Delta, has experienced a marked increase in drowning incidents in recent years, despite the presence of extensive coastal protection structures. While these measures, particularly detached breakwaters (DBWs), groins, and port jetties, were originally implemented to mitigate shoreline erosion, their influence on nearshore hydrodynamics and swimmer safety remains insufficiently understood. In this context, the present study integrates high-resolution bathymetric data, remote sensing observations, and coupled numerical modeling (CMS-Wave and CMS-Flow) to examine how these interventions have altered wave–current interactions. The results indicate that the modified coastal setting produces distinct flow regimes, ranging from weak offshore currents (<0.1 m/s) to moderate rip currents (≈0.25 m/s) within DBW shadow zones, and locally intensified flows exceeding 0.7 m/s in shallow nearshore areas. These conditions facilitate the development of vortices and persistent rip currents, particularly within inter-DBW embayments. A simulation-based swimming risk map was developed by integrating water depth and simulated current characteristics, classifying the coastline into safe, moderate-risk, and high-risk zones. High-risk zones, concentrated within inter-DBW embayments at depths exceeding 2 m, show broad spatial agreement with available drowning and rescue incident records, subject to the limitations of the informal dataset, while the shallow accretional shadow zones landward of the DBWs exhibit comparatively lower hydrodynamic energy and safer conditions. Overall, the study demonstrates that coastal protection structures, although effective in controlling erosion, may unintentionally increase human risk when safety considerations are not incorporated into their design and management. Accordingly, a set of integrated, sustainability-oriented measures is proposed, including enhanced real-time monitoring, regulated beach access, adaptive sand nourishment, and targeted public awareness, with the aim of achieving a more balanced and resilient approach to coastal zone management. Full article

With the large-scale construction of coastal high-speed railways, understanding the mechanical behavior of high-speed railway box girders under tsunami waves has become increasingly important. Existing studies on tsunami-induced forces on bridge girders have mainly focused on T-girders and plate-girders in highway bridges. In contrast, research on high-speed railway box girders, which are characterized by a significant height-to-width ratio, large cantilevers, and complex ancillary facilities on the girder top, remains relatively scarce, especially regarding its behavior under tsunami waves and the effects of lateral displacement on its dynamic response. In light of this, this study focuses on the investigation of the mechanical behavior of a single-track high-speed railway box girder under tsunami waves, and fifth-order solitary waves and dam-break waves are comparatively employed to simulate the typical unbroken and broken tsunami waves. The interaction between tsunami waves and the fixed railway box girder is numerically conducted, and the characteristics of the interaction process and the variation in maximum forces with girder clearance are thoroughly investigated. After that, the numerical interaction between tsunami waves and the laterally movable railway box girder is comparatively carried out, and the lateral displacement effects on the girder wave forces are exhaustively investigated. The results indicate that unbroken and broken tsunami waves exhibit distinctly different interaction processes with the box girder. With decreasing girder clearance, for the unbroken wave, the maximum horizontal and vertical forces occur when the girder bottom and the cantilever root descend to the initial water surface, respectively; for the broken wave, the horizontal and vertical forces simultaneously occur when the girder bottom nears the water surface with a small clearance. Lateral displacement can reduce wave forces on the girder, but the reduction is quite limited—remaining below 10% at the reference stiffness of an actual bearing. It validates that using a fixed girder model to estimate wave forces on an actual laterally movable girder is a slightly conservative and reasonable approach. This study provides further insight into wave forces acting on coastal high-speed railway box girders in tsunami-prone areas. Full article

Monitoring dissolved carbon dioxide (CO₂) in aquatic and sediment systems is critical for understanding carbon cycling and climate feedback. This study develops and characterizes a compact, low-cost microbolometer-based attenuated total reflectance (ATR) mid-infrared sensor for direct dissolved CO₂ measurement in liquid and soil-water environments. The system integrates a ZnSe ATR crystal with custom suspended SiN membrane microbolometers and uses evanescent-wave absorption at 4.26 μm with a broadband LED source and computational spectral reconstruction, eliminating the need for an interferometer. Calibration shows excellent linearity (R² ≈ 0.99) over 50–1000 ppm CO₂, with a practical limit of detection (LOD) of ~26–35 ppm at 5–25 °C. UV-induced CO₂ generation from soil-water mixtures was investigated across UV wavelengths, revealing UV-C (254 nm) as optimal, producing net ΔCO₂ ≈ 339 ppm above ambient levels in 30 min. Environmental factors (temperature 5–35 °C, pH 5–11, pressure 1–1.5 ATM, dissolved organic carbon) were systematically evaluated, confirming robust sensor performance (accuracy >90%, correlation r > 0.98 with reference instrument). This sensor represents the first integration of MEMS microbolometer detectors with ATR evanescent-wave spectroscopy for liquid-phase dissolved CO₂, enabling real-time monitoring and rapid sediment organic carbon assessment in a field-deployable platform. Full article

Large, shallow lakes lacking rooted aquatic vegetation are susceptible to wind-induced wave action that results in increased shear stress on the lake bottom, sediment resuspension and poor water clarity. The relationship between meteorological, hydrographical and sediment characteristics, and sediment dynamics has implications for internal phosphorus cycling and bioavailability, the frequency and duration of harmful cyanobacterial blooms, lake level management and restoration potential. In this study, a multi-parameter water quality sonde was deployed at various sites at the bottom of Utah Lake to measure water quality variables. Sediment cores were collected at each of the deployment sites and analyzed for common physical and chemical properties. Several machine learning regression techniques, including polynomial, decision tree, artificial neural network, and support vector machine, were applied to predict turbidity, a measure of water clarity and surrogate for sediment dynamics, using the observed explanatory variables wind speed and direction, fetch, water depth, sediment properties, algae, and cyanobacteria. The decision tree estimators, random forest and histogram-based gradient boosting had the best model performance, explaining 86–89% of the variability in turbidity when including all the explanatory variables. The artificial neural network estimator multi-layer perceptron and the polynomial regression models also performed well (81%), whereas the support vector machine estimator exhibited poor performance. Chlorophyll and phycocyanin, components of turbidity, were amongst the most important variables to the decision tree and artificial neural network models. Wind speed and water depth were also of high importance, which conforms with mechanistic explanations of sediment mobility caused by wave action and shear stress. Carbonate content was consistently a good predictor due to the calcareous nature of Utah Lake, whereas the importance of the other sediment properties was dependent on the machine learning technique applied. This case study demonstrated the potential for machine learning models to predict water clarity and has promise for more general applications to other shallow lakes and serves as a useful tool for lake management and restoration. Full article

This study investigates the rapid, often uncontrolled urban expansion in Khenchela, a medium-sized city in Algeria’s eastern High Plains, and its profound environmental repercussions amid semi-arid fragility. Drawing on sustainable urban development and resilience frameworks, it dissects pressures such as green space reduction (from 45 ha in 1998 to 33 ha in 2023, dropping per capita from 6.1 m² to 3 m² below WHO standards), water scarcity with 35% leakage losses waste mismanagement, informal settlements on hazardous lands, air/soil pollution, and climate vulnerabilities like heat waves and flooding. Employing a mixed-methods approach documentary analysis of (MPLUUP, LUP and MDP) plans, GIS cartography of spatial evolution (2000–2025), statistical demographics, field observations, and institutional critiques, the research exposes governance gaps: fragmented coordination, weak ecological integration, and resource shortages. It reveals socio-spatial disparities across functional zones, underscoring the need for adaptive, participatory strategies that promote polycentric and compact urban forms, enhanced biodiversity, efficient infrastructure, and inclusive governance to strengthen urban resilience. Full article

The protection of leaves from photoinhibition and berries from dehydration and sunburn has become an increasingly important objective in response to the rising frequency and intensity of heat waves worldwide. This research investigated the effect of a white nonwoven geotextile sheet (TNT) installed in the fruiting zone in the white cultivar ‘Verdicchio’ (Vitis vinifera L.) during critical summer periods with the aim of protecting leaves and berries from extreme heat. The study was conducted over two seasons (2020–2021) in a rainfed vineyard in central Italy using a randomized block design. Physiological and yield parameters were recorded. Vines protected with TNT did not show any changes in net photosynthesis, stomatal conductance, and water use efficiency, compared to unshielded vines. However, TNT reduced leaf temperature and increased berry total acidity and malic acid concentration while reducing sugar content, leading to wines with higher freshness and reduced alcohol levels. The use of TNTs shows significant potential as a practical tool for viticulturists to mitigate the effects of excessive heat, allowing for better management of berry ripening and ultimately improving final wine characteristics. Additionally, TNT is economically feasible, especially if applied only to the afternoon-exposed side of the canopy, and its cost can be amortized, especially in vineyards affected by frequent heat waves and/or dedicated to the production of premium wines. Full article

The mixing process is a critical factor influencing the performance of concrete. As an effective method for enhancing mixing, vibratory stirring relies on the propagation characteristics of mechanical vibration within the concrete matrix. To investigate the propagation behavior of mechanical vibration in fresh steel fiber-reinforced concrete, a custom-developed mechanical vibration source and testing system was established. The results show that the vibration intensity attenuates to 50% at a distance of 5 cm from the source, to approximately 10% at 10 cm, and to less than 3% at 20 cm. A lower water-to-binder ratio facilitates the transmission of the vibration wave, while the presence of fibers and 0–5 mm coarse aggregates hinders vibration propagation. Based on these findings, an input–output energy conservation equation was developed to describe the transmission behavior of vibration energy. The numerical results were compared with experimentally measured vibration power and particle velocity displacement integrals, validating the effectiveness of the proposed energy conservation equation. Full article

Targeting the “Fishtailing Effect” associated with shallow-water, pile-founded column single point mooring (SPM) systems, this study investigates the vessel’s motion characteristics under multiple operational scenarios using a numerical calculation method validated by model tests. A refined classification of combined wind, wave, and current conditions was conducted. The study examines the vessel’s sway and mooring line tension response under both collinear and non-collinear combinations of these environmental forces. Furthermore, methods for suppressing vessel motion were explored. The results indicate that vessel motion leading to the “Fishtailing Effect” is more prone to occur under collinear wind, wave, and current conditions. Wave and wind energy can, to some extent, mitigate the vessel motion. When the current speed exceeds a certain critical threshold, the extreme values of the mooring forces on the swaying vessel undergo an abrupt change. Applying a stern tug force and reducing the mooring line length are both effective in decreasing the vessel motion range and the tension in the mooring lines. The findings shed light on the fishtailing-effect characteristics of tankers moored at pile-founded column SPM systems, providing a valuable reference for the safety and stability design of such mooring systems. Full article

The Zhuanghe coast in the northern part of the Yellow Sea is one of China’s important fishing and ocean engineering areas. Frequent storm surge events pose a significant threat to residents’ safety and properties. This study used the coupled Finite Volume Coastal Ocean Model (FVCOM) and the Surface Wave Model (FVCOM-SWAVE) to investigate storm surges and wave heights during Typhoons Muifa (1109) and Lekima (1909) in the northern parts of the Yellow Sea and analyze the impact of the typhoon parameters on flood inundation on the Zhuanghe coast. The wind stress comparison in the coupled wave–current model uses synthetic wind field data formed by superimposing ERA5 wind fields with a parameterized typhoon model. The results showed that the simulated and measured tide levels, wave heights, and storm surges were in good agreement, indicating that the coupled model accurately reproduced the dynamics of the storm surges and wave heights during the two typhoons. The maximum significant wave height (H_s) exhibited a right-skewed distribution in the two typhoons’ paths, with extreme values consistently located to the right of the typhoon’s center. The decrease in atmospheric pressure at the center of Typhoon Muifa was significantly, nonlinearly, and positively correlated with the severity of storm surge disasters. A significant correlation was observed between the path of Typhoon Muifa and the disaster intensity. Full article