Under the condition of heavy rainfall, the rock and soil saturation of fully weathered granite slope increases, and the shear strength decreases, which is easy to cause slope instability. In this process, the change of matrix suction is the key factor leading to the change of shear strength. Taking Laoshan fully weathered granite slope in Qingdao as the research object, the soil and water characteristic curve (SWCC) of fully weathered granite based on Van Genuchten model was obtained by means of centrifuge test, undrained direct shear test, X-ray diffraction analysis, conventional silicate chemical total analysis test and scanning electron microscope test. The effect of matrix suction on the shear strength of fully weathered granite was studied systematically. The results show these as follows. The saturation of fully weathered granite soil is negatively correlated with matrix suction, and the soil samples with uneven gradation have stronger drainage capacity. The shear strength index is affected by matrix suction differently. Cohesion is more sensitive to the change of matrix suction than the angle of internal friction. There is a positive correlation between matrix suction and shear strength in fully weathered granite soil. The research results can provide theoretical guidance for slope prevention in fully weathered granite area.

In order to study the task-based functional connectivity of the whole brain in schizophrenia patients and healthy controls during task switching, the NSP(nested-spectral partition) method was used to quantify the degree of integration and segregation of the whole brain network and explain differential remodeling patterns of brain networks in schizophrenia patients and healthy controls. Results show that changes in whole-brain functional connectivity patterns in schizophrenia are driven by lower network integration and higher segregation, suggesting global and network-wide local information transfer during task switching in schizophrenia patients efficiency was lower than that of healthy controls. Furthermore, the association between task switching costs (reaction time and switching costs) and task state modularity was analyzed using simple linear correlation. Lower whole-brain modularity and lower salience network modularity in schizophrenia were found to be associated with larger switch costs but not with mean reaction times across the task. In contrast, higher cortical network modularity in healthy control patients was associated with faster task reaction times but not with shorter switch costs. Taken together, the results suggest that quantifying functional network configurations across different task states can provide information about cognitive control performance.

In order to improve the control performance of a doubly-fed wind turbine grid-side converter under unbalanced and harmonic grid voltages, a direct power control algorithm with an improved super-helix fast terminal sliding mode was proposed. First, the mathematical model of the grid-side converter under unbalanced and harmonic grid voltages with power as the state variable was analyzed in a two-phase stationary coordinate system. Then, the power inner-loop design was carried out with a nonlinear expansion state observer for the negative sequence in the mathematical model as well as the disturbances due to each harmonic component. Secondly, to ensure that the system can reach the steady state in a shorter time, the non-singular fast terminal sliding mode surface was constructed and the sliding mode control law for the power inner loop was designed by combining with the improved super-helical sliding mode convergence law. Similarly the terminal sliding mode control rate was also designed for the voltage outer loop. The stability of the non-singular fast terminal sliding mode surface, the improved super-helix control algorithm and the nonlinear expanding state observer was also proved by using the Lyapunov function. Finally, the method was verified to have faster convergence and stronger robustness by comparing it with three different control schemes to perform simulations.

During the production of monocrystalline silicon, defects generated during the crystal pulling process are recognized to severely impact product quality. Traditional visual-based defect detection methods, when applied to the detection of small protrusions in crystal pulling images, are confronted with challenges such as slow detection speeds, large parameter volumes, and difficulties in deployment on embedded terminals. In response to these challenges, an improved YOLOv8 object detection model was proposed incorporating a ContextGuided module to enhance the inference efficiency of the model. An efficient DySample was introduced into the feature fusion network to optimize the efficiency and depth of feature fusion. A lightweight network structure was adopted to reduce the complexity and computational demands of the model, making it suitable for devices with limited computing resources. The model has been trained and tested on an industrial dataset, demonstrating a more accurate detection of small protrusions with a mean average precision (mAP) of 97.7%. Compared to YOLOv8n, it exhibits an increase of 11.6% in precision and a reduction in parameter volume by 31.9%, facilitating its deployment on embedded terminals.

The boundaries of underground geological bodies are effectively highlighted through gravity inversion based on a typical focusing stabilizer, but this process is significantly affected by the focusing factor. The focusing characteristics are possessed by the exponential focusing stabilizer. To a certain extent, the issue of selecting the focusing factor can be circumvented by it, and it has the potential to have improved the effectiveness of three-dimensional gravity inversion.Furthermore, the multiplicity of solutions in inversion can be improved by the constraint imposed by the penalty function, which confine the inverted physical property values within a certain range. Based on this, in order to explore the improvement effects on three-dimensional gravity inversion by the exponential focusing stabilizer and penalty function constraint, the exponential focusing stabilizer and penalty function were incorporated into the three-dimensional gravity regularization inversion objective function. Comparisons were made of the effects resulting from three-dimensional gravity inversion, both with and without the involvement of the exponential focusing stabilizer, as well as with and without the application of the penalty function constraint. Model experiments have demonstrated that: the physical properties and spatial distribution of anomalous bodies can be accurately restored by the exponential focusing stabilizer, but there exist instances where false anomalies arise and physical property values surpass the true values. Situations like these can be improved by the exponential focusing inversion that is based on penalty function constraints. Furthermore, the accuracy of the solution can be enhanced by the zonal processing of penalty function constraints. The above situation indicates that the inversion method based on the exponential-type focusing stabilizer and constrained by penalty functions has certain potential to be generalized.

A significant number of subsalt oil and gas fields are distributed worldwide. Due to the high costs associated with coring operations in salt formations, conducting creep experiments on specific salt rock cores is challenging. To address this issue, a method for creating artificial salt rock cores was developed wherein the degree of recrystallization was controlled by adjusting the preparation temperature and pressure. By testing the acoustic velocity, density, and uniaxial peak strength of salt rock cores under different preparation conditions, the optimal preparation conditions were identified. Creep experiments verified that the artificial salt rock cores exhibit similar creep characteristics to natural salt rock cores, indicating the feasibility of using artificial cores as substitutes for natural ones. Based on indoor creep experiments, a viscoelastic constitutive model of salt rock was constructed. The result showed that the rheological characteristics of the decelerating creep stage conform to the Kelvin model, while the steady-state creep stage aligns with the Heard model. A UMAT subroutine was compiled to describe the creep characteristics of the decelerating and steady-state stages, demonstrating a good fit and indicating the applicability of the viscoelastic model constructed in this study. Creep experiments on composite salt rocks with different contents of anhydrite showed that the presence of anhydrite inhibits the creep of salt rock. The higher the anhydrite content in the salt rock, the lower the creep rate of the rock. Therefore, in salt layers containing anhydrite, the density of drilling fluid used during drilling can be appropriately reduced.

In order to solve the efficiency issues in distributed load responses to frequency regulation commands, an innovative strategy was introduced based on reinforcement learning for load aggregators’ pricing incentives in response to frequency commands. Within this strategy, a game-theoretic model between the load aggregators and load clusters was constructed, and the load aggregators adjust incentive prices based on frequency commands and their pricing strategies, while loads adjust their power consumption based on their own electricity costs to flexibly respond to the frequency commands. The multi-agent soft actor-critic (MASAC) algorithm was used to investigate the solution. The results show that the pricing incentive method enables effective load response to frequency commands, and the use of the MASAC algorithm not only optimizes the decision-making process but also significantly reduces computational complexity, achieving efficient dynamic adjustment. It is concluded that this method provides an effective solution for frequency regulation in power systems, offering significant theoretical significance and practical value.

In order to comprehend the scale and connectivity of sandbodies in late oilfield development, it is imperative to conduct a detailed characterization of fluvial sandbodies in the upper Guantao Formation of Gudong oilfield. Through comprehensive analysis of core, well logging, and seismic data, the sedimentary characteristics of braided river and meandering river were determined under the control of dense well array. The results indicate that the upper Guantao Formation has undergone a sedimentary evolution process from braided river to meandering river. The lower Guantao Formation exhibits braided fluvial reservoir with braid bar, braid channel, and overbank sand microfacies, while the upper Guantao Formation features meandering fluvial reservoir with microfacies types such as point bar, abandoned channel, crevasse splay, and floodplain. By conducting core-log calibration analysis, the logging response characteristics and sandbody development laws of braided and meandering rivers were determined. The channel sandbody of a braided river is cut and overlapped in multiple stages while being distributed across multiple branches on a plane. On the other hand, the meandering fluvial channel sandbody develops in isolation but forms strips on a plane. Under the control of dense well array, we have quantitatively determined the scale of sandbody development for both braided and meandering rivers. Additionally, the relationship between sandbody thickness and width for different river types were established which holds significant guiding significance for identifying sandbody connectivity and 3D geological modeling.

SPH (smooth particle hydrodynamics) and MoorDyn numerical model were used to investigate systematically the dynamic behavior of moored floating bodies on stepped seabed. Based on the comparison with the experimental data, the influence of wave height and step height on the motion response and mooring force of moored box floating body on stepped seabed was discussed in detail. The results show that the motion response of the two floating bodies increases with the increase of wave height. The mooring power of the other three cables also show an increasing trend except for L3. As the height of the ladder continues to rise, the two floating bodies above and below the seabed ladder appear different change rules. In addition, it is found that the relationship between L2 mooring and L0 and L1 is about 3 times, and the relationship between L2 mooring and L3 is about 2 times.

The rod of a fire drive production well in Xinjiang oilfield is seriously corroded, and there are many corrosion pits on the surface. In order to find out the cause of rod corrosion failure, the metallographic structure and physical and chemical properties of the failed rod were tested and analyzed, and the corrosion characteristics were analyzed by scanning electron microscope, energy spectrometer and X-ray diffraction analysis, and the failure causes were found out combined with the service conditions of the rod. The results show that the chemical composition, metalloid structure and inclusions of the D-class rod meet the standard requirements of the rod. The rod has only been in service for 1 year and 8 months and its diameter has decreased from 19 mm to 16 mm, the average corrosion rate is 1.796 mm /a, and the maximum surface corrosion pit depth is 2.1 mm. The surface of the rod is mainly attached with FeCO₃, FeS and CaCO₃. It is judged that the rod is corroded by CO₂/H₂S and underscale corrosion caused by high salinity produced water. At the same time, a large amount of Cl^- in the produced liquid promotes the development of pitting pits. It is recommended to inject corrosion and scale inhibitor into production wells with temperature lower than 50 ℃, pH value between 6 and 8, and formation water belonging to high calcium and high chlorine to protect the D-class rod and extend the service life of the rod.