Search Results (24)

Shallow-buried coal seams in western China are commonly overlain by deeply incised gully terrain, where mining is often accompanied by coal-wall spalling and abnormal increases in support resistance, which affect safe and efficient production. To investigate overburden failure during shallow-buried coal seam mining under gully terrain and to clarify the support–resistance mechanism, a typical working face was selected as the engineering background. Physical similarity simulation, 3DEC numerical simulation, and theoretical analysis were used to analyze overburden failure characteristics and the coupled evolution of the stress, displacement, and fracture fields. Mechanical models of key-stratum fracture and a support–resistance estimation model were established to reveal the influence of overburden-thickness variation on key-stratum fracture and support resistance. The results show that overburden failure in gully areas exhibits pronounced stage-dependent and asymmetric characteristics. In the similarity simulation, the initial fracture intervals of the key stratum in the downhill section were 32 m and 36 m, indicating an asymmetric fracture pattern with a shorter span on the left side and a longer span on the right side. In the uphill section, the periodic fracture interval of the key stratum decreased from 30 m to 24 m as the overburden thickness increased. During overburden failure in gully areas, the three fields exhibited a coupled relationship: stress concentration at the working face caused overburden failure and subsidence, which promoted fracture propagation, whereas stress redistribution in the goaf compacted the fractured overburden and promoted fracture closure. The overburden failure characteristics differed significantly between mining stages. During downhill mining, the key stratum behaved as a fixed-ended beam with a relatively large fracture interval, whereas during uphill mining, it formed a cantilever beam, and its fracture interval decreased with increasing overburden thickness. The loading mechanism of support resistance was shown to be jointly controlled by variations in gully overburden thickness and key-stratum fracture. During downhill mining, support loading increased gradually under the support of the fixed-ended beam key stratum. During uphill mining, support loading exhibited periodic abrupt increases under the combined effects of increasing overburden thickness and periodic fracture of the cantilever-beam key stratum. These findings provide a theoretical basis for strata pressure control at working faces in gully areas. Full article

The structural optimization and mechanical reliability of novel biodegradable JDBM magnesium alloy rib claws were investigated in this study. Simulation analysis, in vitro bending tests, and a 24-week animal implantation experiment demonstrated the promising application potential of the optimized Gen3 magnesium alloy rib claw. Compared with the pre-optimized Gen1 design, finite element analysis (FEA) confirmed that the Gen3 claw—achieved by increasing the width from 6.0 mm to 8.52 mm and adding 1.65 mm transitional fillets at stress concentration zones—resulted in a 54.15% reduction in the maximum von Mises stress (from 116.91 MPa to 53.59 MPa) and a 54.4% decrease in the equivalent strain. In vitro four-point bending tests (ASTM F382-compliant, 11.7 mm span) showed that the Gen3 magnesium claws exhibited a significantly higher yield load (358 ± 21 N) compared with titanium claws (219 ± 16 N; p < 0.05, independent t-test). A 24-week in vivo evaluation in Bama pigs further confirmed the excellent mechanical reliability of the optimized Gen3 magnesium alloy rib claw, and no fractures were observed throughout the implantation period. Full article

Background: Interpersonal violence is one of the most common causes of maxillofacial injuries. These injuries can range from minor soft-tissue injuries to serious, life-threatening conditions. This is particularly important when injuries occur in an exposed and vulnerable area of the body, such as the facial area. This study aimed to analyse the types of maxillofacial injuries, assess a profile of a typical victim of violence and determine the circumstances of the injury. Methods: A retrospective review was performed on the clinical data of patients managed for maxillofacial trauma resulting from interpersonal violence at the Department of Maxillofacial Surgery, University Clinical Hospital, Poznan, spanning the period from 2021 to 2025. Results: The study group included 510 patients, of which 95.41% were males, and the median age in the study group was 34 years. Furthermore, 14.71% of patients were under the influence of alcohol at the time of the violent incident. Most injuries occurred in 2022 (25.88%). Regarding months, June had the highest reported incidents (10.59%), while Saturday was the most injury-prone day (25.10%). The median days of hospitalisation in the study group was five. The mandible was the most frequently affected area. The most common types of fractures were single mandible fractures (30.59%) and double mandible fractures (27.25%). Most injuries were treated surgically (96.67%). In 10.20% of cases, the intervention of other specialists was needed. Conclusions: It is important to effectively prepare medical staff to receive patients with a history of interpersonal violence to diagnose and treat these types of injuries properly. Full article

Background: Elastic stable intramedullary nailing (ESIN) is widely used in pediatric trauma surgery for benefits such as early limb loading, short hospital stays, and easy implant removal. Perioperative antibiotic prophylaxis (PAP) is used to reduce surgical site infections (SSIs). However, the necessity of PAP in minimally invasive pediatric procedures like ESIN remains unclear. Methods: This retrospective analysis reviewed all pediatric fractures treated with ESIN osteosynthesis at a pediatric trauma center over a time span of 10 years. Focus was set on the use of PAP during implantation and complications in the period between osteosynthesis and implant removal, which was used as follow-up. Results: Between January 2013 and December 2023, a total of 979 ESIN osteosyntheses were performed. In total, 4.1% were lost to follow-up resulting in 939 eligible cases. Complications occurred in 14.7% of all cases. However, complications such as wound healing disorders, wound infections, and osteomyelitis were rare, at 1.7%. Between the different subgroups regarding the application of PAP, type of reduction, openness of the fractures, or localization, no significant differences were found. Conclusions: Besides the most minor complications, ESIN osteosynthesis in children and adolescents is safe treatment. No increased risk for complications was observed when closed reduction was performed without the administration of PAP. Full article

Shale oil reservoirs exhibit ultralow permeability and complex pore structures, which result in non-Darcy low-velocity flow and cause permeability to be stress-sensitive. Moreover, two-phase flow of oil and gas frequently occurs during the depletion of shale oil reservoirs. Consequently, investigating the rate-transient behavior of shale oil wells necessitates comprehensive consideration of multiphase flow, threshold pressure gradients, and stress sensitivity. Although numerous analytical models exist for rate-transient analysis of multistage fractured horizontal wells, none of them simultaneously incorporate these critical factors. In this study, we extend the classical five-region model to incorporate multiphase flow, threshold pressure gradients, and stress sensitivity. The proposed model is solved using Pedrosa’s transformation, perturbation theory, the Laplace transform, and the Stehfest numerical inversion method. A systematic analysis of the influence of various parameters on the oil production rate and cumulative oil production is conducted, and a field case study is presented to validate the applicability and effectiveness of the model. It is found that the permeability modulus of the main fracture, the half-length of the main fracture, and the threshold pressure gradient of the unstimulated reservoir have a significant influence on cumulative oil production spanning 20 years. With a 100% relative input error, these parameters result in prediction errors of 23.77%, 16.65%, and 17.78%, respectively. In contrast, the threshold pressure gradient of the main fracture and the threshold pressure gradient of the stimulated reservoir have a negligible impact; under the same level of input error (100%), they cause only 0.36% and 0.48% prediction errors in the 20-year cumulative oil production period, respectively. This research provides an efficient and reliable framework for analyzing production data and forecasting shale oil well performance. Full article

In order to examine the fracture development law of overlying strata in goafs and to reasonably lay out a high gas-drainage roadway under gob-side entry retaining with roadside filling, the 91–105 working face of the Wangzhuang Coal Mine was selected as the engineering case study. The failure laws and fracture development characteristics of the overlying strata in both the strike and dip directions using gob-side entry retaining and roadside filling were studied through rock mechanic tests and PFC numerical simulations. The optimal layout of the high gas-drainage roadway was determined through theoretical analysis and coupled Fluent–PFC numerical simulations, and on-site monitoring was conducted to evaluate the extraction effects. The results indicate that the first weighting interval of the 91–105 working face was 40 m, while the periodic weighting interval was approximately 14 m. The height of the falling zone was 14.4 m, and the height of the gas-conducting fracture zone was 40.7 m. In the dip direction, compared with coal pillar retaining, gob-side entry retaining with roadside filling formed an inverted trapezoid secondary breaking zone above the retaining roadway. Using this method, the span of the separation zone increased to 30 m, and the collapse angle decreased to 52°, resulting in a shift in the separation zone—the primary space for gas migration—toward the goaf. It was determined that the optimal location of the high gas-drainage roadway was 28 m above the coal roof and 30 m horizontally from the return air roadway. Compared with the 8105 working face, this position was 10 m closer toward the goaf. On-site gas extraction monitoring data indicate that, at this optimized position, the gas concentration in the high gas-drainage roadway increased by 22%, and the net gas flow increased by 18%. Full article

Vitiligo, an autoimmune disorder causing depigmented skin patches, includes two types, segmental (SV) and non-segmental (NSV). Previously, NSV was off-label treated using Calcineurine inhibitors (Tacrolimus and Pimecrolimus). In 2022, the FDA approved Ruxolitinib cream, targeting the JAK/STAT pathway for NSV treatment based on promising results. This research conducts a retrospective descriptive safety assessment of Tacrolimus, Pimecrolimus, and Ruxolitinib safety in vitiligo treatment, utilizing the FDA Adverse Event Reporting System (FAERS) database spanning the period from 2013 to 2023 and including patients aged 2 years and above, encompassing both brand and generic names. A total of 844 adverse event reports involving 388 patients were extracted and categorized into dermatological and systemic groups for analysis. Tacrolimus resulted in 12 hospitalizations, two life-threatening events, and four disabilities. Pimecrolimus exhibited urticaria and pigmentation disorders, with tooth fracture as the primary systemic event. Pericarditis was the predominant systemic side effect of Ruxolitinib, followed by anemia, headache, and urosepsis. Local dermatological side effects reported were generally mild, not warranting treatment cessation. In conclusion, vitiligo significantly impacts patients’ psychological well-being, necessitating continuous post-marketing safety monitoring for topical medications. Full article

Background: Peri-implant femoral fractures are increasingly prevalent among the elderly, often leading to re-fractures due to osteoporosis and implant stress. Whole span plating (WSP) has been proposed as a surgical approach to mitigate this risk. Methods: A retrospective study was conducted on 10 patients (mean age: 79.5 years) who underwent WSP for peri-implant femoral fractures between April 2020 and March 2023. Fractures were classified using the Vancouver, NPPIF, and Lewis and Rorabeck systems. Surgical indication required meeting at least two of the following criteria: age ≥ 70 years, history of fragility fracture(s), high fall risk, severe osteoporosis, extensive fracture pattern, or no implant loosening. Results: No re-fractures were observed during a mean follow-up period of 14.5 months. Although 90% of patients required red blood cell transfusions (mean volume: 3.8 units), early weight-bearing was achieved in most cases. Four patients had received osteoporosis treatment, highlighting the need for integrated bone health management. Conclusions: WSP appears to be a feasible and safe surgical option for high-risk patients with peri-implant femoral fractures, potentially reducing the incidence of subsequent fractures. Further studies with larger cohorts and longer follow-up are warranted. Full article

This study systematically performs multi-scale numerical investigation of supercritical CO₂-energized fracturing, widely employed for enhanced oil recovery (EOR) in tight oil and gas reservoirs. Two distinct models, spanning from core scale to field scale, are designed to explore the diffusion patterns of CO₂ into the matrix and its impact on crude oil production at varying scales. The core-scale model employs discrete grid regions to simulate the interaction between fractures and the core, facilitating a comprehensive understanding of CO₂ diffusion and its interaction with crude oil. Based on the core-scale numerical model, the wellbore treatment process is simulated, investigating CO₂ distribution within the core and its influence on crude oil during the well treatment phase. The field-scale model employs a series of grids to simulate fractures, the matrix, and the treatment zone. Additionally, a dilation model is employed to simulate fracture initiation and closure during CO₂ fracturing and production processes. The model explores CO₂ diffusion and its interaction with crude oil at different shut-in times and various injection rates, analyzing their impact on cumulative oil production within a year. The study concludes that during shut-in, CO₂ continues to diffuse deeper into the matrix until CO₂ concentration reaches an equilibrium within a certain range. At the core scale, CO₂ penetrates approximately 4 cm into the core after a 15-day shut-in, effectively reducing the viscosity within a range of about 3.5 cm. At the field scale, CO₂ diffusion extends up to approximately 4 m, with an effective viscosity reduction zone of about 3 m. Results suggest that, theoretically, higher injection rates and longer shut-in times yield better EOR results. However, considering economic factors, a 20-day shut-in period is preferred. Different injection rates indicate varying fracture conduction capabilities upon gas injection completion. Full article

The safety and efficiency of underground coal mining are threatened by thick hard roofs characterized by large overhang areas, problematic spontaneous caving, and high dynamic load upon their breakage. In this study, a mechanical model of the bearing capacity of thick hard roofs in upward mining coalfaces associated with mining activities is built based on bending theories for beams with single generalized displacement and the elastic foundation beam theory. Using this method, we analyze the deformation and fracture mechanisms of a thick hard roof during upward mining. We further derive the mechanical equations of rotational angle, bending moment, shear force, and deflection of the free overhang and coal-bearing zone in the thick hard roof and an equation for calculating the limiting span. The mechanical behaviors of the thick hard roof bearing state are analyzed under different parameters. The results show that the foundation coefficient, roof thickness, and angle of upward mining have little influence on the roof bending moment but are positively correlated to the limiting span. Roof load and overhang length have a significant influence on the roof bending moment. They are negatively and positively correlated with the limiting span, respectively. Finally, a case study is performed on the Ш601 upward mining coalface in the Zhuzhuang Coal Mine. The distribution characteristics of the bending moment of the thick hard roof at different extraction stages are analyzed. At each stage, the limiting spans of the thick hard roof upon breaking were calculated as 13.18, 18.82, and 22.50 m, respectively, being close to the on-site measured periodic weighting lengths of 13.33, 19.33 m, and 22.67 m. This close fit proves the feasibility and accuracy of the developed mechanical model. The present study offers theoretical guidance for estimating the weighting length of thick hard roofs in coalfaces and for engineering technology control in similar scenarios. Full article

Silicate gels have long been utilized as water shut-off agents in petroleum fields to address excessive water production. In recent years, nano-silica gel has emerged as a promising alternative to traditional silicate gels, offering potentially improved plugging performance. However, the long-term effectiveness of these gels remains uncertain, posing challenges to sustained profitability. Therefore, a comprehensive study spanning 6 months was conducted on fractured and induced channel samples treated with nano-silica gel of 75/25 wt% (silica/activator) at 200 °F. A comparative analysis was performed with samples treated using polyacrylamide/polyethyleneimine PAM/PEI gel (9/1 wt%) to compare the performance of both systems. Throughout the aging period in formation water at 167 °F, endurance tests were conducted at regular intervals, complemented by computed tomography (CT) scans to monitor any potential degradation. The results revealed nano-silica gel’s superior long-term performance in plugging fractures and channels compared to PAM/PEI gel. Even after 6 months, the nano-silica gel maintained a remarkable 100% plugging efficiency at 1000 psi, with a maximum leak-off rate of 0.088 cc/min in the mid-fractured sample and 0.027 in the induced channel sample. In comparison, PAM/PEI gel exhibited a reduction in efficiency to 99.15% in the fractured sample (5.5 cc/min maximum leak-off rate) and 99.99% in the induced channel sample (0.036 cc/min maximum leak-off rate). These findings highlight the potential of nano-silica gel as a more durable water shut-off agent for managing water production in fractures and channels. Full article

Introduction: Femoral neck fractures pose significant health risks, particularly in the elderly population, leading to mortality, morbidity, and decreased quality of life. Surgery is the preferred treatment to restore function and alleviate pain, with options including total hip arthroplasty (THA) and hemiarthroplasty (HA). However, clinical guidelines for selecting surgical procedures remain heterogeneous, prompting the need for further investigation into treatment trends and influencing factors. Methods: Data from the NIS database spanning 2016–2019 were analyzed, focusing on patients diagnosed with intracapsular femoral neck fractures and undergoing THA or HA as primary in-hospital surgeries. Advanced statistical analyses using SPSS and MATLAB were conducted to identify trends and factors influencing surgical choices. Results: Comorbidity profiles varied significantly between HA and THA patients, with specific conditions such as Alzheimer’s disease showing higher prevalence in HA patients. Demographic differences included a higher proportion of females and Medicare-insured individuals in the HA group. Racial disparities were observed, with differences in surgical preferences among various ethnic groups. THA adoption gradually increased over the study period, indicating a shift in surgical priorities. Additionally, THA patients tended to be younger on average compared with HA patients. Conclusions: This study highlights evolving trends in surgical management for femoral neck fractures and identifies factors influencing treatment decisions in our cohort. Understanding these trends and disparities is crucial for optimizing patient care and informing future clinical guidelines. Further research should focus on assessing different surgical approaches’ long-term outcomes and cost-effectiveness. Full article

Cracking in concrete box girder bridges will have a significant impact on the safety and durability of the structure, and many box girder bridges which are in service have undergone varying degrees of cracking. Currently, the safety design of actual bridge projects place an emphasis on the stress or the load value of a cross section at the limit value specified in the code for safety control. This design method assumes that the member itself is of uniform and continuous material and is internally undamaged. However, the bridge structure is more or less cracked to varying degrees during the period from casting to construction to operation of the concrete members. In this paper, a finite element computational model of a three-span prestressed concrete box girder bridge with existing cracks is established based on the fracture mechanics theory, and the critical parameters of crack extension are introduced to evaluate the extension state of cracks. At the same time, the extended stability of the existing cracks of the box girder bridge is analyzed by considering the temperature effect, vehicle loading, and prestressing loss, and the sensitivity of crack extension under each working condition is investigated. The results show that, with the increase in crack length and depth, the crack expansion is promoted, but the effect is relatively small, and the maximum stress intensity factor is only 6.48 MPa mm^1/2. Under the multi-factor coupling effect, the cracks show a composite crack expansion dominated by type I cracks, the longitudinal cracks of the existing base plate are in a stable state, the maximum value of the crack expansion critical parameter of the vertical cracks of the webs reaches 1.087, and there is a tendency to expand locally. The maximum value of the critical parameter for crack extension of the vertical crack in the web plate reaches 1.087, and there is a tendency towards local expansion. The crack extension evaluation criteria proposed in this paper have a certain reference value for crack extension research on similar concrete box girder bridges and provide a scientific basis for the optimized design of similar bridges. Full article

During the ice flood period of the Yellow River, the fracture and destruction of river ice can easily lead to the formation of ice jams and ice dams in the curved and narrow reaches. However, the occurrence and development mechanism of river ice fracture remain incompletely understood in the Yellow River. Therefore, based on the three-point bending physical test of the Yellow River ice, a three-point bending fracture numerical model of the Yellow River ice was constructed. The fracture failure process of the Yellow River ice under three-point bending was simulated, and the effects of the crack-to-height ratio and ice grain size on the fracture properties of the river ice were analyzed. By comparing the results with those of physical tests on river ice, it is evident that the fracture model can effectively simulate the cracking process of river ice. Within the confines of the simulated sample size spectrum, as the crack-to-height ratio varies from 0.2 to 0.8, the fracture toughness value of the Yellow River ice spans a range from 115.01 to 143.37 KPa·m^1/2. Correspondingly, within the simulated calculation values ranging from 5.38 mm to 24.07 mm for ice crystal size, the fracture toughness value of the Yellow River ice exhibits a range from 116.89 to 143.37 KPa·m^1/2. The findings reveal that an increase in the crack-to-depth ratio leads to a decrement in the fracture toughness of river ice. Within the scale range encompassed by the model calculations, as the average size of the ice crystal grains augments, the fracture toughness of the river ice exhibits a gradual ascending trend. The research results provide a parameter basis for studying the fracture performance of the Yellow River ice using a numerical simulation method and lays a foundation for investigating the cracking process of river ice from macro and micro multi-scales. Full article

In current energy structure adjustments, the prominence of unconventional oil and gas resources continues to grow, with increasing attention being paid to tight gas, a major component of natural gas production. The Xujiahe Formation gas reservoir in the Western Sichuan Depression represents a typical tight gas reservoir and the study of its reservoir characteristics is a key focus for current and future exploration and development efforts. This review employs the PRISMA method to screen and integrate the primary findings of 26 documents spanning the period from 2008 to 2023, with the aim of providing a comprehensive overview of the progress and outcomes of research on the tight gas reservoir characteristics of the Xujiahe Formation in the Western Sichuan Depression. The selected research documents summarize the characteristics of the Xujiahe Formation tight gas reservoir in the Western Sichuan Depression from four perspectives: lithology, physical properties, reservoir space, and the main factors influencing reservoir quality. Through a review of these previous studies, it is evident that existing research has predominantly focused on the relationship between diagenesis and reservoir densification, indicating certain limitations. We also delve into the characteristics of tight gas sandstone reservoirs in the study area, considering their depositional systems, fracture development, cementation, and impact on the exploration and development of tight gas reservoirs. Additionally, we propose measures to stabilize and enhance tight gas production in the Xujiahe Formation in the Western Sichuan Depression. Moreover, we outline the next steps for further research and exploration. Full article