Search Results (2,302)

In the past three decades, the city of Addis Ababa, a capital city of Africa, has grown significantly in population, facilities, and infrastructure. The area involved in the recent urbanization is prone to slow natural subsidence phenomena that can be accelerated due to anthropogenic factors such as groundwater overexploitation and loading of unconsolidated soils. The main aim of this study is to identify and monitor the areas most affected by subsidence in a context, such as that of many areas of emerging countries, characterized by the lack of geological and technical data. In these contexts, advanced remote sensing techniques can support the assessment of spatial and temporal patterns of ground instability phenomena, providing critical information on potential conditioning and triggering factors. In the case of subsidence, these factors may have a natural or anthropogenic origin or result from a combination of both. The increasing availability of SAR data acquired by the Sentinel-1 mission around the world and the refinement of processing techniques that have taken place in recent years allow one to identify and monitor the critical conditions deriving from the impressive recent expansion of megacities such as Addis Ababa. In this work, the Sentinel-1 SAR images from Oct 2014 to Jan 2021 were processed through the PS-InSAR technique, which allows us to estimate the deformations of the Earth’s surface with high precision, especially in urbanized areas. The obtained deformation velocity maps and displacement time series have been validated using accurate second-order geodetic control points and compared with the recent urbanization of the territory. The results demonstrate the presence of areas affected by a vertical rate of displacement of up to 21 mm/year and a maximum displacement of about 13.50 cm. These areas correspond to sectors that are most predisposed to subsidence phenomena due to the presence of recent alluvial deposits and have suffered greater anthropic pressure through the construction of new buildings and the exploitation of groundwater. Satellite interferometry techniques are confirmed to be a reliable tool for monitoring potentially dangerous geological processes, and in the case examined in this work, they represent the only way to verify the urbanized areas exposed to the risk of damage with great effectiveness and low cost, providing local authorities with crucial information on the priorities of intervention. Full article

The Carboniferous–Permian strata in the Daning–Jixian Block, located on the eastern edge of the Ordos Basin, host multiple sets of tight gas reservoirs. However, systematic research on the characteristics and gas production differences of multilayer tight sandstone gas-bearing systems remains limited. Based on geochemical signatures, reservoir pressure coefficients, and sequence stratigraphy, the tight sandstone gas systems are subdivided into upper and lower systems, separated by regionally extensive Taiyuan Formation limestone. The upper system is further partitioned into four subsystems. Depositional variability from the Benxi Formation to the He 8 Member has generated diverse litho-mineralogical characteristics. The Shan 1 and He 8 Members, deposited in low-energy delta-front subaqueous distributary channels with gentle topography, exhibit lower quartz content (predominantly feldspar lithic sandstone and lithic quartz sand-stone) and elevated lithic fragments, matrix, and clay minerals (particularly chlorite). These factors increase displacement and median pressures, resulting in inferior reservoir quality. By comparing and evaluating the gas production effects under different extraction methods, targeted optimization recommendations are provided to offer both theoretical support and practical guidance for the efficient development of this block. Full article

This study proposes a hierarchical Archimedean copula (HAC) framework to model the complex dependence structures in hydrodynamic landslide deformations, with a focus on the Donglinxin (DLX) landslide. Hierarchical Archimedean copulas, compared to elliptical copulas, offer greater flexibility by requiring fewer parameters while maintaining broader applicability. The HAC model, combined with pseudo-maximum likelihood estimation (PMLE), is applied to analyze the interdependencies among the landslide-related variables, such as monthly displacement increments, reservoir water level fluctuations, groundwater variations, and precipitation. A case study of the DLX landslide demonstrates the model’s ability to quantify the critical aspects of landslide deformation, including variable correlations, risk thresholds, conditional probabilities, and return periods. The analysis reveals a strong hierarchical dependence between monthly displacement increments and reservoir water level drops. The model also provides valuable insights into the potential risk factors, helping to optimize landslide monitoring and early-warning systems for more effective disaster mitigation. Full article

Background: Refugees often experience multiple traumatic events due to persecution, conflict, and displacement, which can result in poor mental health outcomes. Objective: The current study examined whether coping and resilience mediate the relationship between traumatic experience(s) and mental health outcomes and whether these indirect effects were moderated by age, gender, and refugee camp duration. Method: A cross-sectional, correlational study design was employed. Data were collected from 14 July 2019 to 28 August 2019. A sample of 414 adolescent refugees from two refugee camps in the Gambella regional state of Ethiopia were selected using proportional stratified sampling and simple random sampling techniques. Participants completed a self-reported questionnaire. Data were analysed using Structural Equation Modelling for hypotheses testing causal models. Results: Coping and resilience fully mediated the relationship between traumatic experience and mental health among adolescent refugees. Refugee camp duration as a moderator factor weakens the positive relationship between traumatic experiences and mental health outcomes. Conclusions: This study highlights the critical importance of comprehensive intervention strategies that strengthen adolescent refugee personal, family, social, and community level coping and resilience abilities within refugee camps setting. The findings also strongly suggested that early intervention in refugee camps could protect adolescent refugees from possible psychological distress and maintain adolescents’ mental health and well-being within refugee camps. Full article

The fluctuation of reservoir water levels is a critical factor influencing the evolution of reservoir landslide–anti-slide pile systems. To investigate the reinforcement mechanism of anti-slide piles in reservoir landslides under the effect of reservoir water level fluctuations, this study employs numerical simulation methods to establish a three-dimensional slope model, simulating the drawdown process of the reservoir water level from 175 m to 145 m. The displacement and strain fields of the reservoir landslide during the water level drawdown are analyzed. Furthermore, the strain characteristics of the anti-slide pile-reinforced reservoir landslide under stress–seepage coupling are studied, and the prevention effectiveness of the landslide–anti-slide pile interaction system is explored. The results indicate that the drawdown of the reservoir water level can lead to the gradual expansion of the strain and displacement zones in the landslide, as well as a reduction in the safety factor. Under the effect of anti-slide piles, the maximum deformation of the reservoir landslide is significantly reduced. The optimal reinforcement effect is achieved when the anti-slide piles are arranged in the middle of the reservoir landslide, with a pile spacing of four times the pile diameter and an embedded depth reaching the critical depth. The findings of this study can provide a scientific basis for analyzing the instability mechanisms and mitigation of reservoir landslides. Full article

We systematically investigated the anchorage performance of self-drilling anchor bolts in strongly weathered dolomite through integrated field pull-out tests and FLAC3D numerical modeling. The study incorporates symmetry principles in both experimental design and numerical simulations to ensure balanced force distribution and model simplification. Experimental data collected from a slope reinforcement project demonstrated that grouting parameters of 0.8 MPa pressure and 0.8 water–cement ratio achieved an interfacial bond strength of 0.147 MPa, surpassing the recommended value by 22.5%. A modified FLAC3D pile element, calibrated against RS6-01 anchor bolt test data, exhibited improved alignment with load–displacement curves, converging to 272 kN ultimate capacity at 26.1 mm displacement. Symmetrical anchor configurations in the numerical model reduced computational complexity while maintaining accuracy in stress distribution analysis. Through orthogonal experimental design, symmetry-driven parameter optimization identified a 7 m bolt length, 30° installation angle, and 2 m spacing as the most effective configuration. This solution increased the slope safety factor by 19.98% while reducing displacements by 46–62%. The symmetry in anchor spacing and angular alignment contributed to uniform stress redistribution, enhancing slope stability. The findings highlight the synergy between symmetry principles and geotechnical reinforcement strategies. Full article

Conventional oat seeders suffer from poor seeding uniformity, a large coefficient of variation in seed volume, and significant seed wastage. To address these issues, a variable-capacity spoon-type oat precision hill seeder was designed based on the agronomic requirements of oat hole seeding and the structural characteristics of hill seeders. Through force analysis and theoretical calculations, the angular velocity range of the variable-capacity spoon-type oat precision hill seeder was determined to be within 0–6.9 rad/s. An experiment was conducted using the angular velocity of the hill seeder, the inclination angle of the seed guide spoon, and the length of the bridging groove as test factors. The ranges of these factors for optimal seed displacement performance were established. Based on the Box–Behnken test principle, a response surface test was designed using Design-Expert software (Design-Expert 13). Experimental results identified the optimal operating parameters as follows: an angular velocity of 4.9 rad/s for the hill seeder, a guide spoon inclination angle of 71.0°, and a bridging groove length of 10.9 mm. Under these conditions, the qualified rate, leakage rate, and multiple rates were 92.2%, 5.3%, and 2.6%, respectively. The results of the field trial showed that the seeding qualified rate was 91.2%, the leakage rate was 4.6%, and the multiple rate was 4.2%. The errors between the field test results and the simulation test results were −1.0%, −0.7%, and 1.6%, respectively, meeting the requirements for oat seeding. Full article

Background/Objectives: Submacular hemorrhage (SMH) associated with neovascular age-related macular degeneration (nAMD) can lead to significant vision loss, and the optimal management strategy remains uncertain. This study aimed to evaluate the efficacy and safety of pneumatic displacement (PD) without tissue plasminogen activator (t-PA) for SMH secondary to nAMD. Methods: A retrospective analysis was conducted on 22 eyes with SMH secondary to nAMD treated with PD without t-PA. Best-corrected visual acuity (BCVA), central retinal thickness (CRT), number of intravitreal injections, and postoperative complications were assessed at baseline and follow-up. Multiple logistic regression analyses were used to identify factors associated with visual outcomes. Results: In the 22 eyes that completed the 6-month follow-up, BCVA (logMAR) was 0.88 ± 0.46 at baseline and 0.76 ± 0.63 at 6 months (p = 0.24). In the 15 eyes with 12-month follow-up, BCVA improved significantly from 0.92 ± 0.47 at baseline to 0.56 ± 0.51 at 12 months (p = 0.01). CRT significantly decreased at 3 months (p < 0.01). During this period, patients received an average of 8.13 ± 2.90 intravitreal anti-vascular endothelial growth factor (VEGF) injections. A shorter duration from symptom onset to treatment was associated with better visual outcomes (p = 0.02). Postoperative vitreous hemorrhage occurred in 31.8% of cases. Conclusions: PD without t-PA, in combination with anti-VEGF therapy, improved visual outcomes over 12 months. Early intervention and continuous anti-VEGF administration appear to be key factors in optimizing treatment outcomes. Further studies are needed to establish standardized treatment protocols for SMH associated with nAMD. Full article

A novel mechanism for seamless morphing trailing edge flaps is presented in this paper. This bio-inspired morphing concept is derived from an elephant’s trunk and is called the Elephant Trunk Mechanism (ETM). The structural flexibility of an elephant’s trunk and its ability to perform various types of deformations make it a promising choice in morphing technology for increasing the performance of continuous and smooth downward bending deformation at a trailing edge. This mechanism consists of a number of tooth-like elements attached to a solid wing box; the contractions of these tooth-like elements by external actuation forces change the trailing edge shape in the downwards direction. The main actuation forces are applied through wire ropes passing through tooth-like elements to generate the desired contractions on the flexible teeth. A static structural analysis using the Finite Element Method (FEM) is performed to examine this novel morphing concept and ensure its structural feasibility and stability. Topology optimization is also performed to find the optimum configuration with the objective of reducing the structural weight. The optimized mechanism is then attached to the flap section of a UAS-S45 wing. Finally, a skin analysis is performed to find its optimum skin material, which corresponds to the requirements of the morphing flap. The results of structural analysis and topology optimization reveal the reliability and stability of the proposed mechanism for application in the Seamless Morphing Trailing Edge (SMTE) flap. The optimization results led to significant improvements in the structural parameters, in addition to the desired weight reduction. The ETM maximum vertical displacement increased by 8.6%, while the von Mises stress decreased by 10.43%. Furthermore, the factor of safety improved from 1.3 to 1.5, thus indicating a safer design. The mass of the structure was reduced by 35.5%, achieving the primary goal of topology optimization. Full article

Despite the growing human–wildlife interactions (HWIs) globally, little attention has been paid to their effects on women and children, who often bear the brunt of loss of property and livelihoods. A systematic scoping review of four databases was undertaken to map and synthesize English-language evidence on the nature, causes, and impact of human–wildlife interactions on women and children across cultures. The 42 studies retained reveal that the proximity of human habitation to forest areas; expansion, deforestation, and encroachment of animal space; humans’ dependence on forest resources for livelihood; displacement of carnivores; and animals coming into the human space in search for food are the predominant causes of HWIs. Various types of HWIs and widely varying frequencies and durations of HWIs were reported. Individual and collective aspects of physical, psychological, economic, social, and environmental impacts on women and children were identified. The themes extracted were gendered roles, multi-factor vulnerabilities of women, religious beliefs, low participation of women in decision-making, social superstition against tiger widows, and perceptions of coexistence. Attention to perceptions of HWIs in different cultures and societies was limited, with notable gaps in the coverage of women and children and important geographic areas. These findings stress the need to bridge the geographical and cultural gap through multi-disciplinary actions on the determinants and effects of HWIs on women and children. Full article

As a key component of the die-casting machine, the flow linearity of the high-pressure, large-flow proportional throttle valve is a critical factor affecting injection accuracy at low openings. However, under existing main valve structures, flow linearity is typically nonlinear. To address this issue, this paper introduces a main valve structure designed to enhance flow linearity at low openings. Firstly, the working principle of the proportional throttle valve is explained, and the relationship between flow rate and spool displacement is calculated. Secondly, a finite element model of the proportional throttle valve’s main valve flow field is developed. The impact of four primary spool structures on flow linearity is examined, and a small rounded rectangular throttle orifice is proposed. Thirdly, the size of the spool orifice is optimized using an orthogonal test method, and the trend of how different structures’ orifice sizes influence flow linearity is investigated. Finally, a valve prototype is fabricated, and the optimization’s effectiveness is experimentally verified. The results of the throttle valve’s design and optimization provide guidance for future work. Full article

Marine protected areas (MPAs) have been implemented globally to protect marine habitats and enhance biodiversity, often displacing commercial and recreational fishing activities previously occurring in the area. While the ecological impacts of MPAs have been the subject of considerable attention, the economic impacts on the displaced sectors have generally received less consideration. In this study, we examine the impacts of increasing the proportion of fully protected area within a coastal MPA—the Moreton Bay Marine Park in Queensland, Australia—on the economic performance of the fisheries operating in the area. This MPA is relatively unique as it is located adjacent to a major metropolitan area and, hence, heavily used for a range of activities. Analysis of commercial catch data suggests that the commercial fishery has been less impacted than expected by the loss of available area, although this result varies by species. Comparing fishing activity in the Bay with that in adjacent regions (assumed to reflect the counterfactual), we find evidence of strong improvements in fishery performance of the prawn trawl fleet, no significant change in fish net and line fisheries, and a small but significant decline in the performance of crab fishers. The impact on recreational fishing is uncertain as other external factors obfuscate the impacts of the rezoning. Full article

Surface nanopatterning induced by ion beam irradiation allows for the creation of patterns on large areas of a wide variety of materials. However, surface composition plays a crucial role in the process. In this study, we investigate the bombardment of a metallic alloy, specifically an Au-Cu system with different compositions, discussing differences in the formation of patterns compared to pure materials. Mixtures with compositions ranging from 35 to 65 at.% Cu exhibit a dampening effect on ripple height and depth. At intermediate angles of incidence, horizontal displacement is minimized and sputtering maximized; conversely, at grazing angles, sputtering is minimized and horizontal displacement becomes dependent on material mobility. It is, therefore, evident that sputtering determines the patterning for intermediate angles. However, an analysis of the redistribution factor as a function of the angle of incidence shows that the weight of the redistribution is much lower than that of sputtering in alloys of similar composition at grazing angles due to the amorphization process. This point is confirmed by the data on displaced atoms obtained from the relocation cross-sections. Full article

The NT-CEP pile is an innovative type of pile that builds upon the conventional concrete straight-hole cast-in-place pile. It primarily consists of two components: the main pile and the bearing plate. The key factors influencing its load-bearing capacity include the pile diameter, the cantilever dimensions of the bearing plate, and the slope of the bearing plate’s foot, among others. The pile spacing significantly influences the bearing capacity of NT-CEP pile group foundations. The overall bearing capacity of an NT-CEP pile group foundation is not merely the sum of the ultimate bearing capacities of individual piles; rather, it results from the interactions among the pile bodies, the cap, and the foundation soil. Advancing the design theory of NT-CEP pile groups and enhancing their practical applications in engineering requires an in-depth investigation of how different pile spacings influence the load-bearing performance of pile group foundations. This objective can be achieved by exploring the soil damage mechanisms around side, corner, and central piles. This exploration helps in clarifying the influence of pile spacing on the load-bearing performance. Based on research findings regarding the bearing capacity of single and double pile foundations, this paper utilizes ANSYS finite element simulation analysis to model six-pile and nine-pile groups. Because these arrangements are universally adopted in engineering practice, they are capable of accounting for the pile group effect under various pile spacings and row configurations. The nine-pile group comprises corner piles, side piles, and a center pile, enabling a comprehensive analysis of stress variations among piles at different positions. As six-pile and nine-pile groups represent common pile configurations, studying these two types can provide valuable insights and direct references for optimizing pile foundation design. The study systematically investigates the influence of varying piles spacings on the bearing capacity of NT-CEP pile group foundations. It concludes that, as pile spacing decreases, The displacement of the top of this pile increases. thereby enhancing the group piles effects. Conversely, increasing the spacing between piles represents an effective strategy for elevating the compressive capacity of the NT-CEP pile-group foundation. Larger spacing also increases the vertical load-bearing capacity of the central piles, enhances the lateral friction resistance of corner piles, and heightens the load-sharing proportion between the bearing plate and the pile end. Furthermore, increasing pile spacing raises the ratio of load sharing by the foundation soil for both the CEP nine-pile foundation and the CEP six-pile foundation. The reliability of the simulation study has been verified by a visualization small scale model test of a half cut pile. Full article

In this paper, a bidirectional micro-device based on multi-electrothermal co-actuation is proposed for a fuze safety system, combining the advantages of the simple structure, small size, low input voltage, large output, and absence of electromagnetic interference in electrothermal actuators. Based on the working principle of the multi-electrothermal co-actuation device and the mathematical model of the single V-shaped electrothermal actuator established in this paper, the temperature distribution of the V-shaped electrothermal actuator is simulated. In addition, the dynamic response and the effect of geometric factors on the output performance of the multi-electrothermal co-actuation device are analyzed in detail. Furthermore, driving characteristics tests of the electrothermal micro-device are carried out. The experimental findings indicate that a displacement of approximately 258.95 μm with a response time of about 156.51 ms can be achieved by the V-shaped electrothermal actuator when the applied voltage is 1.2 V. In a single cycle, a total displacement of 340 μm is obtained by the co-actuation device in around 1.28 s. Full article