The pore structure is a pivotal determinant of the physical properties of tight sandstone reservoirs, and elucidating its characteristics holds great significance for oil and gas exploration and development. Taking the 4th member of the Xujiahe Formation tight sandstone reservoirs in Tianfu Gas Area as an example, the pore structure characteristics, fractal features, and fluid mobility of the Xu-4 sandstone in the study area were systematically analyzed through thin section identification, scanning electron microscopy observation, nuclear magnetic resonance testing, high-pressure mercury intrusion testing, and X-ray diffraction experiments, combined with fractal theory. The results indicate that the sandstones of the 4th member of the Xujiahe Formation in the study area are predominantly composed of feldspar lithic sandstone, belonging to an ultra-low pore-ultra-low permeability pore type reservoir. The pore type is primarily feldspar-dissolved pores, and the throat type is predominantly sheet throats. According to the morphology of the high-pressure mercury injection curves and nuclear magnetic resonance outcomes, the pore structure of the 4th member of the Xujiahe tight sandstone reservoir is categorized into three distinct types. Among them, the material properties of the I-type samples are the best, with larger pore-throat radii, good connectivity and sorting of pore-throat, strong fluid mobility, and the best reservoir quality. The pore structure and fluid mobility of the fourth member of the Xujiahe tight sandstone reservoir are affected by sedimentary structures and mineral content. Specifically, reservoirs with coarser grain sizes and better sorting demonstrate superior pore structure and fluid mobility. Furthermore, quartz, the primary rigid mineral in sandstones, exhibits resistance to compaction, thereby safeguarding the reservoir pores to a certain extent. However, calcite and clay minerals will occupy pore space, resulting in deterioration of the pore structure and fluid mobility of the reservoir.

In order to improve the accuracy of in-camera parameter calibration and reduce the error caused by inaccurate estimation of corner coordinates, a subpixel iterative corner optimization algorithm was proposed. By modeling the camera image, integrating the distortion mathematical model, and using the subpixel iterative algorithm, the gradient value changes of points in the search window were calculated and the corner coordinates were iteratively optimized to provide more accurate initial values for calibration. Combining with the optimized corner coordinates, Zhang's calibration method was used to solve the internal parameters, and the influence of corner points on the acquisition of diagonal points and camera calibration was discussed through experiments. The calibration accuracy was characterized by reprojection error, and the effectiveness of the iterative algorithm was tested. The experimental results show that the algorithm can effectively improve the accuracy of corner acquisition and the calibration accuracy of camera parameters by using fewer iterations.

In order to compare the clinical effect of different surgical technique of ligamentum flavum in percutaneous endoscopic interlaminar lumbar discectomy. From March 2015 to March 2019, 86 cases of L₅-S₁ lumbar disc herniation (LDH) were analyzed retrospectively. According to the different treatment of ligamentum flavum during operation, the patients were divided into control group (n=55) and modified group (n=31). The age, gender, course of disease, duration of surgery, intraoperative bleeding, hospital stay, and surgical related complications between the two groups of patients were analyzed and compared. One month, three months and six months after the operation, the routine outpatient reexamination and follow-up were carried out. Numerical rating scale(NRS) and modified macnab were used to evaluate the effect of operation. SPSS 19.0 was used to process the data. Mean±SD was used for measurement data. Comparison between groups using independent sample t-test, and analysis of variance of repeated measurement data was used for the NRS score comparison before and after operation. The counting data were expressed in percentage, Fisher exact test or χ² test were used for comparison between groups, and Mann Whitney rank sum test was used for comparison of follow-up time and grade grouping data between groups. The results show that the postoperative pain score of both groups decrease significantly(overall variance within the group F_within=197.477, P=0.001). There is no difference between the two groups (inter group overall variance value F_interg=1.701, P=0.203).The time factor has no effect on the results of the two groups(Interaction effect value F_inter=2.231, P=0.108). The NRS score of the modified group is significantly lower than that of the control group (t=2.086, P=0.046). According to modified Macnab criteria, there is no significant difference between the two groups (distribution of postoperative outcomes U=782.000, P=0.308). It is concluded that the modifiedsurgical technique of ligamentum flavum in the PEILD will not prolong the operation time or increase the amount of bleeding. While removing the herniated intervertebral disc, it can preserve the integrity of the relevant tissue structure, achieve satisfied clinical effect, and conforms to the core concept of minimally invasive surgery.

With the transformation of the modern power system, the application of grid-connected inverters is increasing, and the transient synchronization stability of inverters after disturbance is becoming prominent. Previous research on transient synchronization stability mainly focuses on the dynamic of the phase-locked loop, with less consideration of the impact of outer loop control, resulting in a cognitive bottleneck in understanding transient synchronization mechanism. To address these issues, the grid-following voltage source inverter system was modelled, taking into account the inverter control strategy and limiting elements in detail. Subsequently, the impact of different voltage drops on the stability region of the equilibrium point was analyzed, and the effects of outer loop control proportional integral (PI) and limiting elements on transient synchronization were discussed. The influence mechanism of outer loop control on the transient synchronization stability of inverters was revealed systematically. Finally, the effectiveness of the proposed theory was verified in PSCAD/EMTDC.

The confined space and fluctuating brightness levels inside and outside highway tunnels result in notable disparities in driving behaviors across various sections. It's difficult to achieve differential management of various sections within tunnels due to the challenge of implementing uniform warning and control across the entire roadway. Based on the Tongji road trajectory sharing platform (TJRD TS), continuous microscopic parameters of vehicles were extracted to quantify driving characteristics using eight indicators. This approach was aimed at analyzing the differences in driving behavior and safety risks of vehicles at different tunnel locations. Based on unsupervised learning algorithms, a segmenting method was proposed for highway tunnel sections that considers driving characteristics. Firstly, principal components analysis (PCA) was employed to determine the main features representing driving behavior and traffic safety. Subsequently, the K-means clustering algorithm was utilized to divide the distribution of main features along the tunnel direction into segments. Finally, the rationality of tunnel section division was validated through significance analysis. The results show that the driving behavior and safety vary significantly at different positions within the tunnel. Based on driving characteristics, the tunnel sections are segmented into six parts using PCA-K-means clustering: approach section, entrance section, transition section, middle section, exit section, and departure section. The entrance and transition sections exhibit high variability in speed changes and unstable traffic flow, while conflict frequencies are high in the transition and exit sections, with vehicle deceleration and acceleration reaching peak values of 14.89% and 15.65%, respectively. The research results reveal the evolution pattern of vehicle driving characteristics within tunnels and facilitates effective segmentation of highway tunnels. The research results contribute to the formulation of proactive safety control strategies for tunnel vehicles and the realization of precise vehicle-road cooperative control.

Aiming at the current problem of rail transit feeder buses being affected by competition from shared motorcycles, which has led to a significant loss of passenger flow, the service quality of feeder buses was studied and evaluated in order to enhance the competitiveness of feeder buses. Firstly, a questionnaire was designed to collect passenger satisfaction data, and the object importance of each service index of the feeder bus in the passenger perspective was obtained through the random forest algorithm. The subject importance degree of each service indicator under the experts' perspective was obtained through the analytic hierarchy process(AHP), and the competitive importance degree of the service indicators under the competition with shared motorcycles was obtained. Next, the evaluator weight determination method based on the stakeholder perspective was used to weight the combination of the three importance degrees to obtain the comprehensive importance degree of the feeder bus service indicators, and the importance-performance analysis(IPA) matrix was constructed to classify the indicator improvement priority. Finally, the technique for order preference by similarity to an ideal solution (TOPSIS) was used to confirm the specific priority of the service indicators to be improved by combining the comprehensive importance degree and satisfaction degree. The results show that waiting time, transfer fare and ride congestion are the three most effective indicators for improving the service quality of rail-connected buses, and the priority weights for improvement are 0.368, 0.235, and 0.164, respectively. Among them, the waiting time shows high importance under all three perspectives, and is the most prioritized key factor for improvement. Two service indicators, transfer fare and travel time, have high importance in the expert and competitive perspectives, respectively, suggesting that perspectives other than passenger perceptions can also reveal the key role of different indicators in improving service quality. A proposed comprehensive assessment method based on the importance of service indicators in multiple perspectives and the quantification of improvement priority, which can more accurately assess the service quality of feeder buses and provide the direction of improvement.

The conflict between coal resource extraction and ecological environmental protection is particularly pronounced in the Gaojialiang coal mine of Inner Mongolia. To accurately characterize the deformation extent and evolutionary patterns of mining-induced ground subsidence within the study area, small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology combined with Sentinel-1 radar remote sensing data were utilized to obtain the annual average deformation velocity and time-series cumulative deformation over three primary panels. Additionally, the Kriging interpolation method was employed to predict and supplement data in decoherence regions, ensuring comprehensive coverage of the deformation field. The results show that three distinct subsidence zones are identified, spatially correlated with the mined-out areas of panels 203, 301, and 401, respectively. The subsidence is characterized by slow deformation, with a peak annual average deformation velocity of approximately -34 mm/a. The temporal initiation and spatial propagation of subsidence in the three panels align closely with the actual mining sequence and operational conditions. Among these, panel 401 exhibited the largest subsidence area, covering approximately 4.56 km², with a maximum cumulative deformation of -189 mm, followed by panels 301 and 203 in descending order. Ground fractures identified through high-resolution optical remote sensing imagery are consistent with field investigations, predominantly distributed in the zones of maximum deformation intensity. Based on the deformation characteristics and fractures distribution, three high-risk geohazard zones are delineated within the study area. The primary driver of ground subsidence is attributed to longwall mining activities, while geological structures and precipitation infiltration also contributed to the deformation process. SBAS-InSAR technology has good application effects in monitoring large-scale mining-induced ground subsidence, and can provide crucial technical and data support for geological disaster prevention and ecological environment restoration in Gaojialiang mining area.

In order to study the structural strength of platform fire fighting vehicles, and to address the impact of the structural design of its sub-frame, stabilizers, and booms on the stability and safety of the entire vehicle, ANSYS software simulation was used to study its structural strength, and experimental verification was conducted. A simplified 3D model of the sub-frame with stabilizers, and the booms were established separately, the stress distribution under various working conditions was simulated. Then, an experimental environment was set up for stress testing. The results show that when the entire boom is horizontally extended to the left or right of the fire fighting vehicle, it is more likely to experience the phenomenon of virtual legs, with the values of 22.5 mm and 17.5 mm, respectively. The maximum stress of the boom during the retraction and extension process occurs in the area of the folding arm's variable amplitude hinge point and the overlapping area of the telescopic arm. And the difference between the stress data obtained from experiments and simulations is about 4%. This not only provides good guidance for the security testing of platform fire fighting vehicles, but also verifies the credibility of the simulation method, which is helpful for the structural design and optimization of platform fire fighting vehicles.

In the process of coal seam mining, it is easy to cause problems such as large roof overhang area and long collapse step, which affects the failure form of the surrounding rock of the roadway and the deterioration and failure of the supporting body. In view of the occurrence of thick and hard roofs in the 113105 working face of the Bojiang Haizi Mine and the instability of the narrow coal pillars along the empty roadway, the use of roof cutting and pressure relief is an effective way to effectively solve the problem of roof overhang, and the design of its key parameters has an important impact on the pressure relief effect. In order to explore the influence of different roof cutting pressure relief heights on the roof stress evolution law above the narrow coal pillar along the empty roadway, the effect of lateral roof cutting of roadway was studied by combining theoretical analysis, numerical simulation and field observation. Based on the slip-revolve stability theory of masonry beams, the mechanical model of the roof of the coal pillar under different roof cutting heights was constructed, and the bearing stress distribution equation of the coal pillar after different roof cutting heights was obtained. FLAC3D software was used to simulate the stress distribution and displacement evolution characteristics of the coal pillar roof under different roof cutting heights. The simulation results show that the slitting surface formed after the implementation of roof cutting technology effectively blocks the stress propagation path, and the vertical stress peak value in the coal body on both sides of the roadway decreases, and the pressure relief effect gradually increases with the increase of the roof cutting height, when the roof cutting height reaches 19 m, the stress of the coal pillar roof decreases by 17.22 MPa, and the pressure relief rate is 43.4%. The displacement of the roof of the coal pillar gradually decreases with the increase of the roof cutting height, and the reduction rate gradually decreases. The field test shows that according to the designed roof cutting height, the stress of the surrounding rock is significantly reduced, and the deformation degree of the roadway meets the normal mining requirements.

In order to solve the problems of large heat leakage and unclear stress of the adiabatic support structure in the cryogenic storage tank, a finite element model of a 37.4 m³ storage tank was established by the method of thermal-solid interaction, and the heat transfer, stress and deformation of the tank were analyzed, and the supporting structure was optimized. The results show that the daily evaporation rate of liquid nitrogen is 0.10%/d when the heat leakage through the supporting structure is 62.18 W, and the heat leakage of the supporting structure decreases with the decrease of ambient temperature. The influence of liquid temperature on the storage tank is mainly concentrated in the support structure and the inner tank, and the stress and deformation of the support structure increase greatly after considering the influence of temperature, and the maximum stress of the inner tank is less affected, and the deformation is increased by 11.81 times. When storing liquid hydrogen, the heat transfer of the support structure increases by 26% compared with liquid nitrogen. The topology of the supporting structure under the sliding end was optimized with the minimum heat transfer as the optimization goal. The heat transfer of the “Y” type support structure is reduced by 27.20% and the maximum stress is reduced by 7.73%.