Search Results (8,191)

Moisture generation in the ventilation projects of deeply buried underground corridors affects the underground building environment and personnel health. In order to master the heat and humidity transfer law of underground corridors, this paper establishes a mathematical model by theoretical analysis, and the application of the theoretical model in engineering calculation is verified by a field test. It is found that the ventilation efficiency and heat and humidity transfer effect are related to corridor shape. The results show that under the same cross-sectional area, the average temperature drop and humidity of a rectangular corridor are 0.25% and 0.3% higher than that of an arch corridor, and 0.8% and 0.9% higher than that of a circular corridor. Under the condition of constant section circumference, the average temperature drop and humidity of a rectangular corridor are 0.51% and 0.62% higher than that of an arch corridor, and 1.37% and 1.58% higher than that of a circular corridor. When the equivalent diameter is the same, there is almost no difference in the heat and humidity transfer effect of the three shaped corridors. Full article

In recent years, perovskites have quickly gained popularity in applications related to photonic devices and in photovoltaic applications. Over the last several years, the efficiency of photovoltaic (PV) cells based on perovskites has matched the efficiency of PV cells based on silicon. CsPbBr₃ perovskite is gaining more and more popularity, but due to the too large band gap value, its use in photovoltaics is difficult. Another perovskite, very intensively researched and giving hope for further development of photovoltaics, is CsPbI₃. The CsPbI₃ band gap is smaller than the CsPbBr₃ band gap and more suitable for photovoltaic applications. However, CsPbI₃ is unstable under the conditions of solar cell operation. To reduce the band gap value and increase the perovskite stability, very intensive research, both theoretical and experimental, is devoted to structures with mixed halides, i.e., a mixture of bromine and iodine with the general formula CsPbBr_xI_3−x. Computational methods based on DFT have been successfully used for many years to determine the parameters and properties of materials. The use of computational methods significantly reduces the costs of the research performed compared to experimental techniques. The aim of this work is to understand the band gap changes based on DFT calculations as well as XRD and UV-Vis experiments for CsPbBr₃, CsPbI₃, and CsPbBr_xI_3x perovskites. Full article

Coal mine water hazards are one of the five major natural disasters in mines, and water in depleted areas is the most serious form of water hazard causing casualties. The exploration of depleted areas, especially old tunnels, presents significant challenges, and achieving the required borehole density for exploration in depleted areas is difficult in reality. The authors of this paper previously applied for a patent titled “Water Injection Exploration Method for Depleted Areas Based on Stress Seepage Principle”. In order to theoretically analyze the feasibility of the patented results and validate them in practice, we first analyze the stress distribution and seepage phenomena around the goaf theoretically, construct boreholes underground in Renlou Coal Mine, conducting on-site water injection tests for different zones (depleted areas, old tunnels, and general boreholes), and perform transient electromagnetic observations during the water injection tests. A total of 355 sets of water injection flow rate and pressure data were obtained from different zones in three different boreholes; permeability coefficients were calculated based on the measured data, and relevant diagrams were drawn. Through the analysis of water injection test data and theoretical analysis, the following conclusions were drawn: there are disturbances and stress reduction zones around depleted areas (old tunnels), and when the equivalent normal stress induced by water injection pressure is greater than zero, the permeability of fractures will increase significantly. Whether it is a borehole aimed at depleted areas or old tunnels, it shows the characteristic that the closer the distance to the depleted areas (old tunnels) is, the smaller the water injection pressure, and the larger the permeability coefficient. When water is injected into the disturbance and stress reduction zones of the depleted areas (old tunnels), the water injection pressure can decrease from 9–10 MPa to 3–4 MPa, and the permeability coefficient may even increase in quantity value. The phenomena of pressure reduction and increased permeability during water injection are significantly observable, indicating that the water injection exploration method for depleted areas based on the stress seepage principle is feasible and has practical significance. Full article

A theoretical study, based on ab initio electronic structure calculation, is performed in a group of 16 pentacoordinate Dy-SIMs. Theoretical results provide a reasonable explanation of the observed SMM performance based on a concise criterion, i.e., the co-existence of long τ_QTM and high U_eff. To have the desired electronic structure favoring good SMM performance, the contribution from the equatorial coordinating atoms might be even more important than that from the axial coordinating atoms. Widening the axial ∠O–Dy–O might be a probable way to improve the SMM performance of pentacoordinated Dy-SIMs. Starting from existing systems, a rigid-scan type exploration indicates the possibility of U_eff higher than 1600 K. Full article

To address the issues of limited adaptability and low spatial utilization in traditional rigid actuators, a biomimetic actuator with water-induced helical deformation functionality was designed. This actuator is capable of adaptive gripping and retrieval of objects in a narrow lumen. A numerical model was established to analyze its helical deformation mechanism, and the helical deformation characteristics of the actuator were calculated under different structural parameters. Based on four-dimensional (4D) printing technology, which integrates three-dimensional printed structures with responsive materials, experimental samples of biomimetic actuators were fabricated by combining thermoplastic polyurethane fiber scaffolds with water-absorbing polyurethane rubbers. By comparing the simulation results with the experimental data, the numerical model was corrected, providing theoretical guidance for the structural optimization design of the actuator. The experiment shows that the biomimetic actuator can act as a gripper to capture a small target in a lumen less than 5 mm in diameter. This research provides a theoretical and technical foundation for the development of specialized actuators aimed at narrow spaces. Full article

In recent years, many scholars have carried out a large number of theoretical studies on mechanism systems with joint clearances. Some scholars have conducted relevant experiments with simple planar mechanisms, for example, which have proved the feasibility and applicability of the numerical dynamics calculation method and different contact force models to a certain extent. In order to verify the correctness of the theoretical analysis method of the system dynamics considering coating and joint clearances in the previous stage, this paper independently designed and built the RSSP experimental platform of the spatial four-bar mechanism by taking the shear fork mechanism of the soybean picking and separating machine in farming operations, and measured the dynamic changes in the execution components and the wear depth of the spherical shell surface in different working conditions. The effectiveness of the coating on alleviating vibration, reducing joint wear, and extending the working life of the system mechanism was verified. The experimental conclusions provide strong data support for the subsequent effective and long-life operation of the soybean picking and sorting integrated machine. Full article

The positioning of lithium battery tabs in electric vehicles is a crucial aspect of the power battery assembly process. During the pre-tightening process of the lithium battery stack assembly, cells and foams undergo different deformations, leading to varying displacements of cells at different levels. Consequently, determining tab positions poses numerous challenges during the pre-tightening process of the stack assembly. To address these challenges, this paper proposes a method for detecting feature points and calculating the displacement of lithium battery stack tabs based on the MicKey method. This research focuses on the cell tab, utilizing the hue, saturation, and value (HSV) color space for image segmentation to adaptively extract the cell tab region and further obtain the ROI of the cell tab. In order to enhance the accuracy of tab displacement calculation, a novel method for feature point detection and displacement calculation of lithium battery stacks based on the MicKey (Metric Keypoints) method is introduced. MicKey can predict the coordinates of corresponding keypoints in the 3D camera space through keypoint matching based on neural networks, and it can acquire feature point pairs of the subject to be measured through its unique depth reduction characteristics. Results demonstrate that the average displacement error and root mean square error of this method are 0.03 mm and 0.04 mm, respectively. Compared to other feature matching algorithms, this method can more consistently and accurately detect feature points and calculate displacements, meeting the positioning accuracy requirements for the stack pole ear in the actual assembly process. It provides a theoretical foundation for subsequent procedures. Full article

This paper presents the results of a study on the formation of nanostructures of electrochemical titanium oxide for neuromorphic applications. Three anodization synthesis techniques were considered to allow the formation of structures with different sizes and productivity: nanodot, lateral, and imprint. The mathematical model allowed us to calculate the processes of oxygen ion transfer to the reaction zone; the growth of the nanostructure due to the oxidation of the titanium film; and the formation of TiO, Ti₂O₃, and TiO₂ oxides in the volume of the growing nanostructure and the redistribution of oxygen vacancies and conduction channel. Modeling of the nanodot structure synthesis process showed that at the initial stages of growth, a conductivity channel was formed, connecting the top and bottom of the nanostructure, which became thinner over time; at approximately 640 ms, this channel broke into upper and lower nuclei, after which the upper part disappeared. Modeling of the lateral nanostructure synthesis process showed that at the initial stages of growth, a conductivity channel was also formed, which quickly disappeared and left a nucleus that moved after the moving AFM tip. The simulation of the imprint nanostructure synthesis process showed the formation of two conductivity channels at a distance corresponding to the dimensions of the template tip. After about 460 ms, both channels broke, leaving behind embryos. The nanodot, lateral, and imprint nanostructure XPS spectra confirmed the theoretical calculations presented earlier: in the near-surface layers, the TiO₂ oxide was observed, with the subsequent titanium oxide nanostructure surface etching proportion of TiO₂ decreasing, and proportions of Ti₂O₃ and TiO oxides increasing. All nanodot, lateral, and imprint nanostructures showed reproducible resistive switching over 1000 switching cycles and holding their state for 10,000 s at read operation. Full article

As a graphene-like material, h-BN has stimulated great research interest recently due to its potential application for next-generation electronic devices. Herein, a systematic theoretical investigation of electronic structures and optical properties of C-doped and Cu-Al co-doped h-BN is carried out by the first-principles calculations. Firstly, two different C-doped h-BN structures for the para-position and ortho-position are constructed. The results show that the C ortho-doped h-BN (BCN) structure with a band gap of 3.05 eV is relatively stable, which is selected as a substate to achieve the Cu-Al co-doped h-BN. Based on this, the effect of the concentration of C atom doping on the electronic and optical properties of Cu-Al co-doped BC_xN (x = 0, 11.1% and 22.2%) is investigated. The results demonstrate that the band gap of Cu-Al co-doped BC_xN decreases and the optical properties improve with the increase in C atom concentration. The band gap and static dielectric constant of Cu-Al co-doped BC₀N, BC₁N and BC₂N are 0.98 eV, 0.87 eV and 0.23 eV and 2.34, 3.03 and 3.77, respectively. As for all Cu-Al co-doped BC_xN systems, the adsorption peak is red-shifted, and the peak intensity obviously decreases compared to the undoped h-BN. Additionally, the Cu-Al co-doped BC₂N exhibits the best response to visible light. This work will provide valuable guidance for designing and developing h-BN-based doping systems with good performance in the field of optical and photocatalysis. Full article

With the rapid development of e-commerce, the traditional trade mode of forest products has undergone significant changes. Logistics as a key factor to support e-commerce trade is particularly important to build a reasonable e-commerce logistics model of forest products. In the logistics service industry, the issue of cooperative profit allocation of logistics alliance has been crucial and prevalent. However, logistics alliances often face the problem of incomplete information, such as the ambiguity of transportation cost and driving distance, which makes it difficult to effectively apply many classical cooperative game solutions. Therefore, this paper introduces an improved Shapley value for cooperative games in fuzzy situations regarding unclear profit allocation in e-commerce logistics alliance of forest products. This value maximizes the satisfaction of the players by minimizing the contribution excess, according to which the trapezoidal fuzzy number least square contribution is calculated. Based on this, we replace the marginal contribution of the classical Shapley value with this least square contribution, thus creating the improved Shapley value with trapezoidal fuzzy numbers. Through the verification of actual cases, this method not only has theoretical value, but also provides effective guidance for the actual profit allocation of e-commerce logistics alliance of forest products, which helps to promote the stability and sustainable development of alliance. Full article

Aiming to address the challenges of determining the coal pillar’s width and managing the significant deformation of the surrounding rock in the deep gob-side entry driving, the limiting equilibrium zone theory, employing the operational area of Dongpang Mine 21110 as the engineering setting, states that a coal pillar’s appropriate width in the gob-side entry driving falls between 7.9 and 9.8 m. The pattern of vertical stress distribution and the extent of the plastic zone in the roadway for coal pillar widths of 7.0 m, 8.0 m, 9.0 m, and 10.0 m are analyzed, respectively, investigated using the numerical simulation method of FLAC^3D. The acceptable coal pillar width in the deep gob-side entry driving is 8.0 m. Combined with the roadway surrounding rock borehole inspection results, the fracture development condition of the roadway’s full-face surrounding rock is determined, and the asymmetric aberration characteristics, with significant surrounding rock damage depth at the coal pillar flank location, are obtained. Based on the theoretical calculations, an integrated proposal for a “non-symmetrical bolt and cable anchor” coupling support scheme for the surrounding rock in the gob-side entry driving is put forward. This was applied at the Dongpang coal mine site. Engineering practice shows that leaving an 8.0 m coal pillar width and adopting the “non-symmetrical bolt and cable anchor” support system design can control the deformation of the surrounding rock in the track entry at a reasonable range, which ensures the stability of the surrounding rock in the gob-side entry driving. Full article

In wireless power transfer systems, the relative positional misalignment between transmitting and receiving coils significantly impacts the system’s mutual inductance characteristics, thereby constraining the system’s output power stability and transmission efficiency optimization potential. Hence, accurate formulas for calculating mutual inductance are crucial for optimizing coil structures and achieving mutual inductance stability. This study focuses on the mutual inductance characteristics of rectangular coils under positional misalignment conditions in a dual-sided electromagnetic shielding environment. Initially, the research deduces the incident magnetic flux density induced by the current in rectangular coils through the dual Fourier transform and magnetic vector potential method. Subsequently, Maxwell’s equations and boundary conditions are employed to analytically examine the induced eddy currents within the shielding layer, allowing for the calculation of reflected magnetic flux density. Based on these analyses, the study derives a formula for mutual inductance using the magnetic flux density method. A prototype was built for experimental verification. The experiment results show that the maximum error between the measured mutual inductance and the calculated result is less than 3.8%, which verifies the feasibility and the accuracy of the proposed calculation method. Simulations and empirical validation demonstrate the superior accuracy and practicality of the proposed formula. This research not only offers an innovative technological pathway for enhancing the stability and efficiency of wireless power transfer systems but also provides a solid theoretical foundation and guiding framework for coil design and optimization. Full article

Hydraulic fracturing changes the stress state of the coal body, and the residual water within the coal body after fracturing affects its permeability characteristics. To examine the impact of hydraulic measures on the permeability of coal under varying water contents and radial stress distributions, permeability tests were conducted using the improved LFTD1812 triaxial permeameter. The flow rate of coal under different water content combinations was measured, and the permeability, pressure gradient, and seepage velocity of the samples were calculated. The relationships among porosity, permeability, pressure gradient, and seepage velocity were analyzed. The effect of water content on permeability was evaluated, and the directional behavior of permeability was identified. The results showed that the porosity of the samples with water contents of 25%, 17.5%, and 10% decreased by 48.5%, 23.9%, and 17.6%, respectively, during the loading process. The permeability of all samples ranged from 1.91 × 10⁻¹³ m² to 76.91 × 10⁻¹³ m². As the absolute value of the pressure gradient increased, the downward trend of permeability was categorized into three stages: rapid, slow, and stable. Higher water content corresponded to lower initial permeability, with the permeability–pressure gradient curve shifting downward. Additionally, the slow decline zone moved to the right, and the absolute value of the pressure gradient required to enter this zone decreased. Seepage velocity consistently decreased with increasing water content across all osmotic pressure levels, although the rate of decline progressively weakened. The maximum permeability difference between the forward and reverse samples was 10.48 × 10⁻¹³ m². Permeability directionality decreased with increasing equivalent water content and osmotic pressure, with water content identified as the primary influencing factor. Permeability variations caused by axial compression were divided into three phases: the weak influence of the polarization effect, the transition phase, and the strong influence phase. These findings confirm that water content has the most significant impact on permeability, demonstrating that gas flow primarily follows the principle of distance priority toward the nearest borehole. Boreholes closer to the source exhibit higher extraction volumes. These results provide theoretical support for improving coal permeability, enhancing gas drainage efficiency, and preventing gas accidents through hydraulic measures. Full article

In recent years, climate change has increased the frequency of extreme rainfall events, significantly impacting surface water quality (SWQ). This study focuses on Hangzhou, utilizing rainfall data from June 2021 to May 2024 to calculate a series of rainfall extreme indices (REIs). It explores the spatiotemporal variations in these REIs alongside SWQ parameters, including water temperature (WT), dissolved oxygen (DO), pH, total phosphorus (TP), total nitrogen (TN), and turbidity. This research also analyzes the correlations between SWQ parameters and REIs for the first time. The results show that extreme rainfall events primarily occur in July, with increases in both intensity and frequency during the study period. Influenced by human activities, natural conditions, and environmental policies, SWQ parameters in Hangzhou exhibit notable spatiotemporal variability. Correlation analyses reveal significant positive relationships between TP, TN, and turbidity in most areas with REIs. However, the correlations between pH, WT, and turbidity with REIs differ between the eastern and western regions, resulting from variations in land use. These findings will provide a theoretical basis for developing models to predict changes in SWQ based on REIs, contributing to the safeguarding of surface water quality. Full article

Compared to conventional reservoirs, the abundant nanopores developed in unconventional oil and gas reservoirs influence fluid properties, with nano-confinement effects. The phase behavior, flow characteristics, and solid–liquid interactions of fluids are different from those in conventional reservoirs. This review investigates the physical experiments, numerical simulations, and theoretical calculation methods used in the study of nano-confinement effects in unconventional oil and gas energy. The impact of different methods used in the analysis of fluid phase behavior and movement in nanopores is analyzed. Nanofluidic, Monte Carlo method, and modified equation of state are commonly used to study changes in fluid phase behavior. Nano-confinement effects become significant when pore sizes are below 10 nm, generally leading to a reduction in the fluid’s critical parameters. The molecular dynamic simulation, Monte Carlo, and lattice Boltzmann methods are commonly used to study fluid movement. The diffusion rate of fluids decreases as nanopore confinement increases, and the permeability of nanoscale pores is not only an inherent property of the rock but is also influenced by pressure and fluid–solid interactions. In the future, it will be essential to combine various research methods, achieve progress in small-scale experimental analysis and multiscale simulation. Full article