Search Results (119)

Well cementing is an important step in oil and gas development. It uses cement to seal the formation and the casing, preventing fluid leakage. However, when conducting offshore oil well cementing operations, deep-water formations are usually weakly consolidated soils, and it is difficult to form a good cementation between the cement and formation. Therefore, enhancing the strength of the formation is one of the effective measures. This study uses the microbial-induced carbonate precipitation technology to cement sandy formations containing clay minerals. The triaxial tests were conducted to evaluate the consolidation effectiveness in the presence of three clay minerals: montmorillonite, illite, and kaolinite. X-ray computed tomography was utilized to characterize microscopic pore parameters, while thermogravimetric analysis, X-ray diffraction, and surface potential measurements were applied to analyze the mechanisms of clay minerals affecting microbial consolidation. The results showed that microbial mineralization mainly affects the cohesion of the samples. The cohesion of the montmorillonite sample increased from 20 kPa to 65.4 kPa, an increase of up to 3.27 times. The other two samples (illite and kaolinite) had increases of only 0.33 times and 1.82 times. Although the strength of the montmorillonite sample increased the most, unexpected large pores appeared with a diameter of over 120 µm, accounting for 7.1%. This is mainly attributed to the mineral expansion property. The expansion of the minerals will trap more microorganisms in the sample, thereby generating more calcium carbonate. And it also reduced the gaps between sand particles, creating favorable conditions for the connection of calcium carbonate. Although the surface charge of the minerals also affects the attachment of microorganisms, all three minerals have negative charges and a difference of no more than 0.84 mV (pH = 9). Therefore, the expansion property of the minerals is the dominant factor affecting the mechanical and microstructure of the sample. Full article

Utilizing a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach, this study constructs a comprehensive three-dimensional numerical model to simulate particle migration dynamics within rough artificial fractures subjected to the high-energy impact of water inrush. The model explicitly incorporates key governing factors, including intricate fracture wall geometry characterized by the joint roughness coefficient (JRC) and aperture variation, hydraulic pressure gradients representative of inrush events, and polydisperse sand particle sizes. Sophisticated simulations track the complete mobilization, subsequent acceleration, and sustained transport of sand particles driven by the powerful high-pressure flow. The results demonstrate that particle migration trajectories undergo a distinct three-phase kinetic evolution: initial acceleration, intermediate coordination, and final attenuation. This evolution is critically governed by the complex interplay of hydrodynamic shear stress exerted by the fluid flow, frictional resistance at the fracture walls, and dynamic interactions (collisions, contacts) between individual particles. Sensitivity analyses reveal that parameters like fracture roughness exert significant nonlinear control on transport efficiency, with an identified optimal JRC range (14–16) promoting the most effective particle transit. Hydraulic pressure and mean aperture size also exhibit strong, nonlinear regulatory influences. Particle transport manifests through characteristic collective migration patterns, including “overall bulk progression”, processes of “fragmentation followed by reaggregation”, and distinctive “center-stretch-edge-retention” formation. Simultaneously, specific behaviors for individual particles are categorized as navigating the “main shear channel”, experiencing “boundary-disturbance drift”, or becoming trapped as “wall-adhered obstructed” particles. Crucially, a robust multivariate regression model is formulated, integrating these key parameter effects, to quantitatively predict the critical migration time required for 80% of the total particle mass to transit the fracture. This investigation provides fundamental mechanistic insights into the particle–fluid dynamics underpinning hazardous water–sand inrush phenomena, offering valuable theoretical underpinnings for risk assessment and mitigation strategies in deep underground engineering operations. Full article

Wind-blown sand concentrations decay rapidly and in an orderly manner with height above the surface. The saltation flux profiles are of interest to understand wind and sand interactions and for fundamental measurement and modeling of associated transport rates. This study compares methods to measure and represent aeolian sand flux profiles. We measured vertical flux profiles and used quality-controlled data to test power, logarithmic, and exponential functions to reproduce the profiles. These results are used in a pragmatic assessment of the efficiency of reproducing flux profiles from vertically discontinuous arrays of traps or sensors compared to profiles obtained from continuous vertical arrays of segmented traps. Our analysis corroborates previous findings demonstrating that exponential decay functions are statistically the best method to approximate flux profiles. The results are used in a novel application to compare flux profiles reproduced from vertically discontinuous arrays of devices with those obtained from continuous vertical arrays comprising nine mesh-style traps. The results indicate that discontinuous arrays of 3, 4, 5, or 6 devices deployed less than 200 mm from the surface will effectively reproduce results from the continuous array, with average errors less than 3%. Errors increase when devices are at greater heights or as the number of devices decreases. Discontinuous arrays typically do not capture creep transport which would contribute to error in our comparisons. Therefore, creep must comprise less than 3% of total aeolian sand flux, contradicting typical assumptions of 25%. Full article

Leishmaniasis is a zoonotic disease caused by protozoa of the genus Leishmania, transmitted by phlebotomine sand flies. Understanding the feeding behavior and infection rates of these vectors is crucial for disease surveillance and control. We aimed to investigate the natural infection rate of Leishmania spp. in phlebotomines and analyze their blood-feeding patterns in one of the priority areas of the state of São Paulo for the implementation of insecticide-impregnated dog collars. Sand flies were collected from urban and peri-urban areas between 2022 and 2024 using CDC light traps, manual aspiration, and Shannon traps. PCR was used to detect Leishmania DNA (SSU rDNA gene), and blood meal sources (COI gene). A total of 414 sand flies were collected, with 222 engorged females analyzed for blood meals and 192 specimens tested for Leishmania spp. infection. The predominant blood source was humans (67%), followed by chickens (64.1%), and dogs (18.9%), considering that 45.1% of the samples presented mixed blood meals. Leishmania infantum was found in 1% of the samples. These findings highlight the feeding plasticity of sand flies and their potential role in disease transmission, reinforcing the need for continuous epidemiological surveillance and vector control strategies, particularly the implementation of insecticide-impregnated dog collars. Full article

In hydropower tunnel systems, unlined pressurized tunnels in competent rock are commonly used for cost-effective construction. Incorporating pressurized sand traps at the downstream end of these tunnels can increase plant capacity and improve energy efficiency. The present work focuses on optimizing the performance of existing pressurized sand traps. Hydraulic scale models were developed and tested at the Hydraulic Laboratory of NTNU, Within the 960 MW Tonstad Hydropower Plant in southern Norway as a case study. This study compares 1:1 velocity/sediment scaling with Froude scaling through physical experiments, analyzing velocity profiles via Particle Image Velocimetry (PIV) and sediment trap efficiency. Results show that Froude scaling, combined with geometric sediment scaling, provides superior accuracy in trap efficiency scaling across varying factors. However, in many practical hydropower applications, the large scaling factor required for laboratory models results in very small model sediments, leading to cohesion limitations. In such cases, Froude scaling may not be feasible. The 1:1 scaling method provides a conservative alternative. Hence, for practical applications, 1:1 scaling may be more cost-effective and sufficient for designing pressurized sand traps. This study emphasizes the importance of accounting for unscaled parameters and flow phenomena in hydraulic model design. Full article

Hybrid metaheuristic algorithms have been widely used to solve global optimization problems, making the concept of hybridization increasingly important. This study proposes a new hybrid multi-strategy metaheuristic algorithm named COSGO, which combines the strengths of grey wolf optimization (GWO) and Sand Cat Swarm Optimization (SCSO) to effectively address global optimization tasks. Additionally, a chaotic opposition-based learning strategy is incorporated to enhance the efficiency and global search capability of the algorithm. One of the main challenges in metaheuristic algorithms is premature convergence or getting trapped in local optima. To overcome this, the proposed strategy is designed to improve exploration and help the algorithm escape local minima. As a real-world application, multi-level thresholding for color image segmentation—a well-known problem in image processing—is studied. The COSGO algorithm is applied using two objective functions, Otsu’s method and Kapur’s entropy, to determine optimal multi-level thresholds. Experiments are conducted on 10 images from the widely used BSD500 dataset. The results show that the COSGO algorithm achieves competitive performance compared to other State-of-the-Art algorithms. To further evaluate its effectiveness, the CEC2017 benchmark functions are employed, and a Friedman ranking test is used to statistically analyze the results. Full article

Methane hydrate is a crystalline compound in which methane is trapped within a water lattice under high-pressure, low-temperature conditions. Its presence in oceanic and permafrost sediments makes it a promising alternative energy source, but also a potential contributor to climate change. Accurate in situ detection remains a major challenge due to hydrate’s dispersed occurrence and the limitations of conventional geophysical methods. This study investigates the feasibility of using the associated alpha particle (AAP) technique for the direct detection of methane hydrate. A series of laboratory measurements was conducted on sand-based samples with varying levels of methane hydrate simulant. Using a 14 MeV neutron generator and a LaBr₃ gamma detector, the 4.44 MeV carbon peak was monitored and calibrated against volumetric hydrate saturation. The minimum detection limit (MDL) was experimentally determined to be $(67\pm 25)\%$. Although the result is subject to high uncertainty, it provides a preliminary benchmark for evaluating the method’s sensitivity and highlights the potential of AAP-based gamma spectroscopy for in situ detection, especially when supported by higher neutron flux in future applications. Full article

The viability and host-seeking behavior of Strongyloides larvae are significantly influenced by soil conditions, emphasizing the critical role of environmental control in disease management. This is particularly relevant given the growing concerns about drug resistance resulting from mass chemotherapy or the use of chemical nematicides. Strongyloides stercoralis was effectively inactivated by exposure to 50 °C for both 12 and 24 h (long-term exposure). Strongyloides ratti was inactivated by 50 °C for 20 min (short-term exposure), 9% saline for 50 min, and a combination of 4% saline and 40 °C for 50 min. The combined treatment successfully inactivated S. ratti in four soil mediums using 5% saline at a central temperature of 40 °C. Thermotaxis responses to noxious heat revealed attraction at 40 °C, increased localized searching at 45 °C, and complete inactivation at 50 °C. Larvae migrating within agar at 45 °C were more readily inactivated. Long-range heat attraction at 5 cm resulted in the inactivation of up to 50% of incoming larvae; however, heat-high concentration saline traps at 3 cm distance proved ineffective. Thermal–saline agar trapping demonstrated promise for larval removal in sand, loam, and laterite soils. This method offers a promising approach to larval removal while minimizing hazards to non-target organisms. Full article

Railway transportation is a critical component of global infrastructure which plays a significant role in ensuring the safe movement of goods and people. In desert environments, the effectiveness of railway transportation heavily relies on addressing key challenges such as shifting sand, migrating dunes, wind erosion, and sand deposition, which can disrupt operations and increase maintenance costs. To mitigate the significant threats posed by windblown sand to railway safety along the Lanzhou-Xinjiang High-Speed Railway, the technique of double rows of sand fences constructed from concrete columns and plates has been applied to the windward side of the railway. These structures are designed to reduce wind speed and capture moving sand, protecting the rail infrastructure. These fences reduce wind velocity on their leeward sides by 78% and 87% for the first and second rows, respectively. Additionally, due to the large openings in the fences, the sand-trapping efficiencies are 72% for the first row and 63% for the second. The effective shelter distance of the fence is ten times its height. However, advanced technologies like geographic information systems (GIS), geothermal energy solutions, and sustainable infrastructure practices are increasingly integrated into railway transportation to mitigate these risks and enhance safety and reliability. For the Etihad Railway, GIS techniques were utilized to identify areas vulnerable to sand accumulation and validate the substantial benefits of sand fences. Notably, a 40% reduction in wind speed and a significant 74% decrease in sand flux were observed post-installation, underscoring the effectiveness of these structures in disrupting sand mobility. Specifically, wind speed after fence installation was reduced by 40%. The threshold velocity for sand transport was approximately 0.206 m/s. The sand flux before fence installation was 19.95 kg/m²/s, reduced to 5.175 kg/m²/s after fence installation, marking a 74% reduction. The sand deposition behind the sand fence over a 500 m section was around 7387.5 kg/s. This demonstrates the significant role that sand fences play in reducing wind-driven sand transport, thus protecting the Etihad Railway from sand accumulation, and maintaining operational safety. Full article

The eighth member of the Permian Shihezi Formation is one of the main tight sandstone gas layers in the Longdong Area of Ordos Basin, and the source rocks are dark mudstones and shales located in the Shanxi Formation and Taiyuan Formation of the Permian. The tight muddy sandstone at the top provides shielding conditions and constitutes traps. The lithology is mainly lithic quartz sandstone, followed by lithic sandstone. The reservoir space is mainly dissolved pores, inter crystalline pores, intergranular pores and so on. Clay minerals are the main interstitial materials, and chlorite has the highest content in it, a product of alkaline, moderate- to high-temperature, reducing conditions, effectively inhibited quartz cementation and enhanced secondary porosity development during mesodiagenesis. The average porosity of the reservoir is about 4.01%, and the average permeability is about 0.5 × 10⁻³ μm³, which is a typical low porosity and ultra-low permeability tight reservoir. The thickness of the sandstone reservoir in the study area is from 5 m to more than 25 m, mainly in the NE direction. The sand bodies are distributed in lenses on the plane. Full article

This paper proposes an Enhanced Dynamic Sand Cat Search Optimization algorithm (EDSCSO) designed to address the high-order nonlinearities and strong coupling issues in the parameter tuning of the position sliding mode controller for electro-hydrostatic actuators (EHAs). Traditional swarm intelligence optimization algorithms often struggle with the transition from global to local search, which leads to being trapped in local optima and results in lower computational efficiency. To overcome these challenges, the EDSCSO algorithm introduces an escape mechanism, a stochastic elite cooperative bootstrap strategy, and a multi-path differential perturbation strategy. These enhancements significantly increase the diversity of the population, facilitate a smooth transition from global to local search, avoid local optimum traps, and better balance the exploration and exploitation capabilities of the algorithm. Based on this algorithm, the sliding mode surface and convergence rate parameters within the sliding mode controller are optimized. Simulation validations conducted on the combined platform of MATLAB/Simulink and AMESim demonstrate that the sliding mode PID controller optimized by the EDSCSO algorithm achieves smaller steady-state and tracking errors, exhibits greater robustness, and offers enhanced computational efficiency compared to other swarm intelligence optimization algorithms. This study provides an effective optimization strategy to improve the control performance of the EHA position sliding mode controller. Full article

Here, we discuss the results of an experiment in toe-line protection of estuarine embankments from frequent slope failure using silt traps. We test the feasibility of terracotta rings to trap silt and promote natural mangrove regeneration in barren patches in front of embankments around human settlements in the Indian Sundarban region, designated as the Sundarban Biosphere Reserve. The initial results of the first sixteen months of observations, between May 2023 and August 2024, are encouraging. Sediment accumulation in the silt traps across sites ranges between 4 and 42 cm. Periodic granulometric analyses of sediments indicate that while the middle estuarine sites accumulate more clay/silt, the lower estuarine sites accumulate more sand. During the late and post-monsoon seasons, all sites except one, on the eastern coast of the lower estuarine island, exhibit natural mangrove regeneration, the main species being Porteresia coarctata, Sueda maritima and Avicennia marina. Additionally, oysters Saccostrea cuculata and occasionally Crassostrea cuttakensis are found attached to the terracotta silt traps. The results highlight the potential of the nature-based Living Shoreline strategy to support mangrove regeneration and toe-line protection cost-effectively. The study also successfully opens up new possibilities for sustainable elevation management in the sinking and shrinking mangrove region of the Sundarbans, a significant development in the face of climate change and accelerated sea level rise. Full article

The fourth member of the Triassic in the Tahe Oilfield, as one of the key strata for clastic rock reservoirs, poses significant challenges to oil and gas exploration due to unclear identification of its depositional environments and sedimentary microfacies. Based on the guidance of sequence stratigraphy and sedimentological theories, this study comprehensively analyzed well logging data from more than 130 wells, core analysis from 9 coring wells (including lithology, sedimentary structures, and facies sequence characteristics), 3D seismic data (covering an area of 360 km²), and regional geological background. Combined with screening and settling method granularity experiments, the sedimentary characteristics of the sand body in the fourth member were systematically characterized. The results indicate the following: (1) In the Tahe Oilfield, the strata within the fourth member of the Triassic are predominantly characterized by marginal lacustrine subfacies deposits, with delta-front subfacies deposits developing in localized areas. (2) From the planar distribution perspective, influenced by the northwestern provenance, a small deltaic depositional system developed in the early stage of the fourth member in the northwestern part of the Triassic Akekule Formation. This system was dominated by subaqueous distributary channel sand bodies, which were subjected to erosion and reshaping by lake water, leading to the formation of several stable sand bars along the lake shoreline. In the later stage of the fourth member, as the lake level continued to recede, the area of deltaic deposition expanded westward, and deltaic deposits also developed in the central to slightly eastern parts of the study area. Based on this, a depositional model for the fourth member of the Triassic in the Tahe Oilfield has been established. (3) In the Tahe Oilfield, the sand bodies within the fourth member of the Triassic system gradually pinch out into mudstone, forming lithological pinch-out traps. Among these, the channel sand bodies and long belt sand ridges, due to their good sorting and high permeability, become favorable reservoirs for oil and gas accumulation. This study clarifies the sedimentary model of the fourth member and reveals the spatial differentiation mechanism of sand bodies under the control of lake-level fluctuations and ancient structures. It can provide exploration guidance for delta lake sedimentary systems similar to the edge of foreland basins, especially for efficient development of complex lithological oil and gas reservoirs controlled by multistage lake invasion–lake retreat cycles. Full article

Durum wheat (Triticum turgidum subsp. durum), though less widespread than soft wheat, is crucial in Mediterranean countries. Agriculture significantly contributes to global climate change by emitting greenhouse gases, particularly nitrous oxide, which accounts for about 6% of global warming because of its long atmospheric lifetime and heat-trapping capacity. Soil fertility is influenced by the interplay of its physical, chemical, and biological properties, which, in turn, affect the production of nitrous oxide (N₂O), a potent greenhouse gas. The yield-scaled N₂O emission index, which measures N₂O emissions relative to crop yield, is used to develop sustainable agricultural strategies. Our study aimed to compare the effects of organic vs. conventional fertilization on durum wheat yield and N₂O emissions across three soils differing in texture. The study was carried out from autumn 2020 to spring 2021 in Portici (Naples, Italy). A factorial combination was applied, involving three different texture classes (clay, sand, and loam) and four fertilization strategies (no fertilization, compost, digestate, and mineral fertilization). Our results highlight that in sandy soil, wheat yield reached its highest values, particularly under digestate fertilization (+74.5%) and, interestingly, with lower cumulative N₂O emissions (−16%). However, in sandy soil, the protein content of kernels was lower, similar to that recorded for the fertilization with digestate. Full article

To overcome the consequences of arsenic contaminations, several methods are being proposed. However, practical implementation of those studied methods is rare, mainly due to uncertainties in perception regarding the treatment efficiency of a particular method under different operating conditions. A parametric mathematical model is proposed for the estimation of arsenic-trapping efficiency using saxaul ash sand as adsorbent for the treatment of arsenic-contaminated water under different input conditions. The developed model is based on three independent factors: adsorbent dose concentration, solution pH and initial arsenic concentration in the solution. These factors were selected based on a rigorous experimental study using saxaul ash as adsorbent, which was conducted earlier. Individual relationships between each of those contributing factors and arsenic-removal efficiencies were established based on experimental results. Each relationship was expressed with a best-fit equation and converted to a contributed factor. It is found that the derived best-fit relationships of removal efficiencies follow polynomial patterns with pH and logarithmic patterns with initial concentration and dose concentration. Finally, all the contributed factors were amalgamated into a single equation representing arsenic-removal efficiency for any pH, initial arsenic concentration, and dose concentration. Model-predicted results are compared with the original measured data from the earlier experiments. It is found that the developed best-fit equations for pH, initial arsenic concentration and dose concentration can replicate measured values with coefficient of determination values of 0.88, 0.96 and 0.99, respectively. A comparison of final equation predictions reveals that the predictions are quite accurate, except for a few estimations yielding general statistical errors such as RMSE = 8.07, MAE = 4.73 and RAE = 0.10. Discrepancies in a few predicted values can be attributed to the non-adherence of original measured values to the adopted best-fit trend, especially for the case of pH. Such a developed model can be used for the estimation of arsenic-trapping efficiency with any desirable mix of independent variables selected in this study. Full article