Search Results (75)

The Chang 8 tight oil reservoir in the Xifeng area of the Ordos Basin is characterized by poor reservoir properties, making conventional water flooding ineffective for efficient reservoir development. CO₂ flooding is therefore considered an important approach for enhancing oil recovery in tight reservoirs. However, suitable development strategies for direct CO₂ injection in undeveloped reservoir areas remain insufficiently understood. In this study, compositional numerical simulation combined with a single-factor sensitivity analysis was employed to investigate the effects of key parameters, including well pattern configuration, fracturing parameters, injection–production strategy, and gas injection modes. The results indicate that an inverted nine-spot well pattern with vertical well injection and vertical well production, a well spacing of 500 m, and a row spacing of 200 m can achieve relatively favorable areal and vertical sweep performance. A fracture half-length of 80 m, fracture widths of 0.003–0.005 m, and fracturing treatment before initial production help balance early-stage productivity and gas channeling control. Maintaining an injection rate of 0.03–0.04 PV/a, an oil production rate of 2–3 m³/d, and a bottomhole flowing pressure of 13–14 MPa is beneficial for maintaining reservoir energy and stabilizing displacement-front propagation. Based on neighboring field development experience, switching from continuous CO₂ injection to water–alternating–gas (WAG) injection during the mid-development stage can improve mobility control and enlarge the CO₂ swept volume. Under the current geological model and simulation conditions, the recommended development strategy predicts a recovery factor of 35.43% over a 30-year production period. The results provide reasonable parameter ranges and an engineering reference for direct CO₂ flooding development in the Chang 8 tight oil reservoir and similar reservoirs. Full article

Aiming to investigate the unclear lower limit of microscopic pore mobilization during CO₂ pre-fracturing in the shale oil reservoirs of the Ma51X well block, this study integrates high-temperature and high-pressure (110 °C 70 MPa) CO₂ huff-n-puff with nuclear magnetic resonance (NMR) experiments. The results demonstrate the following: (1) under high-temperature (110 °C) and ultra-high-pressure (70 MPa) conditions, the lower limit of mobilizable pores for CO₂ to displace reservoir crude oil reaches 1.7~2.2 nm; (2) the dominant mobilized pore range for CO₂ is 5.1~38.5 nm, and macropore abundance directly dictates the macroscopic sweep coverage of CO₂; (3) the modification effect of CO₂ on pore structure is primarily concentrated within the mesopore-to-macropore systems, and with an increase in huff-n-puff cycles, crude oil in mesopores progressively migrates toward macropores; and (4) multi-cycle CO₂ huff-n-puff exhibits a cyclic performance pattern characterized by dominance in the initial cycle and subsequent attenuation. This study precisely delineates the lower limit of mobilizable pores for crude oil in the shale oil reservoirs of the Ma51X well block, providing a robust theoretical foundation for the efficient development of this formation and analogous ultra-low permeability reservoirs. Full article

Municipal leadership has become increasingly central to addressing global challenges such as war-related displacement, migration governance, and climate change, reflecting a broader shift toward polycentric and networked forms of multilateralism. This study examines how cities have expanded their international roles over the past decade, responding to governance gaps with pragmatic, people-centred action. Using a qualitative, theory-informed comparative case study design, it draws on three original case studies grounded in direct practitioner experience: European municipal cooperation supporting Ukraine during war; city engagement in shaping the Global Compact for Migration; and municipal leadership in advancing climate action and the emerging climate mobility agenda. Across these cases, the analysis identifies consistent patterns of multi-scalar municipal agency, including decentralized humanitarian action, norm-setting in international negotiations, and innovations in multilevel climate governance. Cities leverage transnational networks—such as the Mayors Migration Council and the C40 Cities Climate Leadership Group—to amplify political influence, exchange solutions, and secure resources, even as fiscal pressures and political polarization increasingly constrain local capacity. It concludes that cities are becoming important actors in shaping global governance, yet their effectiveness depends on institutionalized representation, enhanced fiscal autonomy, and stronger protections for local leaders. Embedding municipalities more fully within evolving multilateral architectures can better align global commitments with local implementation and improve the resilience and legitimacy of international policy coordination. Full article

We analyse pebble RFID tracing observations to investigate sediment transport dynamics in gravel-bed rivers using statistical modelling. This study examines a dataset of nearly 3500 tracer displacement measurements collected during 27 sediment-mobilizing events in a pre-Alpine reach in Italy. Our analysis follows three main steps, addressing tracer mobility patterns, event-scale transport dynamics, and reach-scale bedload inference. First, using Markov Chain analysis of state transitions on typical and high-magnitude transport events, we demonstrate that pebbles tend to maintain their mobility state between events, characterizing the between-event intermittency of bedload transport. A subsequent analysis of flow characteristics reveals that consecutive floods of similar magnitude exhibit increasing movement probability while maintaining similar virtual velocities. Finally, we train Gradient Boosting regression models to estimate distributions of pebble displacements and virtual velocities (defined, following common usage, as the ratio between the distance a tracer travels during a mobilising event and the duration of that event). Together with Monte Carlo propagation, these models are used to derive reach-scale volume estimates. The models identify flow rate and event duration as primary controls, while grain size has minimal influence within the sampled range of tracer dimensions. To strengthen our approach, we implement an extensive multi-stage validation process aimed at both single-tracer predictions and overall basin-scale movement estimates. The results indicate that high-magnitude transport events (12% of observations) contribute similar bedload volumes as typical events (88% of observations), highlighting the significant role of extreme events in total sediment transport. Model predictions yield bedload volume estimates that align well with independent measurements from a downstream sediment retention basin. Full article

Coastal reclaimed areas are characterized by complex strata and high groundwater levels, and pile foundations in such areas often suffer from insufficient uplift resistance. Compared with conventional cast-in-place piles, squeezed branch piles exhibit superior uplift performance; however, studies on squeezed branch piles in reclaimed areas remain limited. To investigate the uplift bearing performance of squeezed branch piles in the complex strata of coastal reclaimed areas, in situ full-scale uplift tests were conducted in the Shenzhen Binhai Avenue (Headquarters Base Section) traffic reconstruction project. Based on the actual physical and mechanical properties of the soil strata, a three-dimensional numerical model was established and validated against the load–displacement curves obtained from the in situ full-scale uplift tests. On this basis, the uplift bearing performance of squeezed branch piles, the differences in uplift bearing performance between branch and plate structures, and their applicable strata were analyzed. The plate structure and different branch configurations of squeezed branch piles exhibit distinct symmetric configuration characteristics, and these configuration differences influence the overall uplift bearing performance. The results show that the load–displacement curves of the uplift piles are generally smooth, without obvious abrupt rises or drops, exhibiting a gradual variation pattern, and the maximum pile-head displacements are all less than 100 mm. The mobilization of the bearing capacity of the branch and plate structures exhibits a distinct temporal and sequential pattern, with the plate structures at shallower embedment depths mobilized earlier than those at greater depths. Compared with conventional cast-in-place pile foundations, the presence of branches and plates endows squeezed branch piles with better elastic mechanical behavior and higher rebound ratios during unloading. Under identical stratum and loading conditions, the uplift bearing performance of the plate is 133% higher than that of the six-radial-branch configuration, while that of the six-radial-branch configuration is 34% higher than that of the four-radial-branch configuration. It is recommended to adopt the six-radial-branch configuration in clayey sandy gravel strata and the plate configuration in gravelly clayey soil and completely weathered coarse-grained granite strata, whereas neither branches nor plates are recommended in soil-like strongly weathered coarse-grained granite strata. Full article

Background/Objectives: The uprighting of mesially tipped mandibular second molars following first molar loss is a complex surgical and orthodontic challenge. Conventional methods often result in reciprocal anchorage loss. Mini-implants (MIs) have emerged as essential temporary anchorage devices (TADs) that provide absolute anchorage and enable more predictable tooth movements. Methods: Numerical simulations were performed to evaluate the forces required for mandibular second molar uprighting under two conditions: first, only with the second molar present, and second, with both the second and the third molars present. Although the periodontal ligament exhibits nonlinear and viscoelastic behavior in vivo, a linear elastic approximation was adopted to allow for a reliable evaluation of comparative stress distribution and initial displacement patterns within the scope of this exploratory biomechanical study. Stress distribution in the roots, periodontal ligament, and alveolar bone was assessed for each scenario. Two three-dimensional (3D) models of the left mandibular segment were created from scans of a human mandible and its teeth. The first model included the canine, the first and second premolars, and the second molar. A second model additionally incorporated the third molar. A retromolar MI was placed in both models. Molar uprighting was simulated using a spring connecting the implant to a button bonded on the mesial surface of the second molar. A force of 200 g was applied because in clinical orthodontic practice, forces that exceed approximately 2 N may cause pain or undesirable tooth mobility. Displacements along the X, Y, and Z axes, as well as regions of peak stress, were analyzed. Results: Model 1 showed maximum displacements at the furcation/mid-root, distal root apex, and distal crown, with von Mises stresses of 0.470 to 0.371 MPa. In Model 2, peak displacements occurred at the mesial root and crown, with stresses of 0.185 and 0.149 MPa, respectively. The magnitude of displacements was in the order of 10⁻⁵ mm. Such values represent initial mechanical responses rather than clinically observable tooth movements. However, the differences between models (e.g., the stress reduction) are expected to be clinically meaningful. Conclusions: Since clinical measurements regarding the stress distribution on teeth and surrounding tissues during orthodontic molar uprighting movements are impossible to perform, the finite element method (FEM) can offer insight into these aspects. The presence of the third molar significantly modulates the biomechanics of second molar uprighting via retromolar MIs. When the third molar is present, the second molar exhibits a reduced tendency for deformation during distalization, although this leads to a slower displacement. This FEM provides biomechanical insights but does not support direct clinical decision-making. The present findings should be viewed as theoretical biomechanical tendencies that require confirmation through clinical, experimental, and longitudinal studies before translation into clinical practice. Full article

Accurate prediction of user mobility patterns is essential for location-based services and intelligent transportation systems. In this study, we propose a sequence modeling framework that utilizes Gated Recurrent Units (GRUs) to predict future geographic coordinates (latitude and longitude) from user trajectory data stored in CSV format. By constructing input sequences of past GPS positions and training the GRU network to estimate the next position, we achieve robust trajectory forecasting performance. Experimental evaluation demonstrates that the GRU-based approach consistently yields higher prediction accuracy than the conventional Long Short-Term Memory (LSTM) model under the same conditions. The results highlight the effectiveness of GRUs in handling sequential spatial data with reduced computational complexity, suggesting their suitability for real-time and resource-constrained location prediction tasks. The models are evaluated on real-world GPS trajectory data consisting of over 800 sequential location samples, using distance-based metrics including MAE, RMSE, Average Displacement Error (ADE), and Final Displacement Error (FDE) to assess prediction accuracy in meters. This study proposes an enhanced GRU model, representing a key innovation and the main contribution of our work. The primary contribution of this study lies not merely in comparing GRU and LSTM models, but in proposing an enhanced GRU architecture that integrates motion features and an attention mechanism for improved GPS trajectory prediction. Unlike prior studies focusing solely on model comparison, our approach demonstrates methodological advancements through attention-based feature weighting and validated performance in real-world autonomous vehicle experiments. Full article

Background: Floating barbed threads are commonly used for minimally invasive midface lifting and rely on mobile subcutaneous tissue for support, which may limit stability. Fixation is primarily achieved by barb engagement within the subcutaneous fat and fibrous septa of the retinacula cutis. Objectives: To describe an anatomically guided modification of the APTOS Excellence Visage Soft (PLLA/PCL) thread technique, positioning the terminal segment posterior to the zygomatic retaining ligament line with the aim to enhancing mechanical stability. This technical report presents the anatomical rationale, procedural steps, and illustrative clinical cases demonstrating feasibility. Methods: The modified technique uses a single-entry point at the superior zygomatic margin, with five threads per hemiface. After linear insertion, the cannula is rotated laterally and inferiorly to position the terminal barbs posterior to the zygomatic retaining ligament line, thereby transferring tensile load toward a more fixed anatomical structure. Representative cases were documented and are presented. Results: Illustrative cases showed immediate midface elevation with improved malar projection and softening of the nasolabial and mentolabial folds. Standardized 3D imaging and vector analysis demonstrated a superolateral pattern of soft tissue displacement along the intended vectors, consistent with the proposed fixed-anchorage concept. The procedure was well tolerated, with only mild and transient local effects observed. One illustrative case included photographic follow-up at 12 months, in which preservation of midface contour and malar projection was visually appreciable. Conclusions: Redirecting the terminal thread segment posterior to the zygomatic retaining ligament line is a feasible modification that may contribute to improved vector stability by engaging a fixed fascial structure. Observations—including one case with 12-month follow-up—support the anatomical plausibility of the approach, although controlled studies with objective endpoints are necessary to confirm long-term efficacy and reproducibility. Full article

The convergence of climate change, migration, and health represents a critical global challenge, with the Middle East and North Africa (MENA) region illustrating acute vulnerabilities while offering insight relevant beyond the region. Increasing exposure to extreme heat, droughts, and floods drives displacement, constrained mobility, and adaptive migration, placing additional pressure on already stretched health systems. This paper proposes an integrated Nexus Action Framework for Climate Change, Migration, and Health (NAF-CMH) to address these interlinked dynamics and move beyond fragmented, sector-specific responses. The framework conceptualizes human mobility both as a potential resilience strategy and as a determinant of health, encompassing climate-affected migrants, displaced populations, and those experiencing involuntary immobility across diverse pathways and settings. It promotes systematic integration of health considerations into climate adaptation and migration governance and situates these interventions within the broader agenda of climate-resilient health systems. Drawing on a non-systematic narrative review of peer-reviewed and grey literature, complemented by the authors’ expertise, the paper identifies seven interrelated pillars for coordinated policy and operational action. While grounded in MENA-specific vulnerabilities, the framework is flexible and adaptable to other regions facing climate-driven mobility challenges. By providing an operational architecture for multisector collaboration, the NAF-CMH supports policymakers, public health authorities, and migration actors in strengthening resilience, reducing vulnerability and safeguarding health amid accelerating climate impacts and evolving mobility patterns. Full article

Integrating enhanced oil recovery (EOR) with geological carbon storage presents a dual-strategy solution for sustainable hydrocarbon production and greenhouse gas emission mitigation. CO₂ flooding, particularly under miscible conditions, is a pivotal technology in this endeavor. This study employs advanced in situ nuclear magnetic resonance (NMR) imaging to visually and quantitatively investigate the pore-scale mechanisms of CO₂ flooding in fractured carbonate rocks from a Kazakhstan oilfield. By establishing a novel correlation between NMR data and pore throat size distribution, we quantify the lower limit of pore throat mobilization—a key parameter for evaluating storage and displacement efficiency. Results show that miscible CO₂ flooding significantly reduces this limit to the submicron scale (0.1 μm) in matrix rocks, dramatically improving oil recovery from small pores. However, fracture networks dominate fluid flow, leading to early gas breakthrough and severely limiting CO₂ penetration and miscible displacement in the matrix. The study provides pore-scale insights for optimizing CO₂ injection strategies to maximize both hydrocarbon recovery and CO₂ storage potential in complex carbonate formations. The study elucidates the microscopic mobilization mechanisms and remaining oil distribution patterns during CO₂ flooding in volatile reservoirs. Moreover, it represents an environmentally friendly methodology for mitigating greenhouse gas emissions. Full article

Inflatable structures have attracted increasing attention in recent years due to their light weight, translucency, rapid assembly or disassembly, mobility, and self-cleaning performance. Meanwhile, their flexible characteristics and low-damping behavior render the structures prone to significant deformation and vibration under wind and snow loads and may even lead to structural failure. Therefore, numerous researchers have conducted in-depth investigations into the mechanical response of such structures under wind and snow loads. However, existing studies on inflatable structures subjected to wind and snow loads have mainly focused on an air-supported form, and the mechanical behavior of inflatable ribbed arch structures has not yet been sufficiently investigated. To investigate the mechanical behavior and deformation patterns of inflatable ribbed arch structures subjected to wind and snow loads, static tests were conducted on three specimens with varying spans, heights, and cable arrangements. Following inflation to an internal pressure of 250 kPa and preloading with the tarpaulin weight, the wind load and snow load were converted to the equivalent concentrated loads and applied in five incremental stages. Displacement monitoring points (DMPs) were tracked using a total station. Under the wind load, a consistent wind-induced deformation pattern was observed across specimens characterized by inward displacement in Region I, upward displacement in Region II, and negligible change in Region III. The maximum horizontal displacements of Specimens A, B, and C were 76 mm, 140 mm, and 249 mm, respectively. Under snow load, the upper sections of all three specimens experienced significant downward displacement, while both sides demonstrated a slight tendency for outward expansion and upward lift. The maximum vertical displacements of Specimens A, B, and C were −27 mm, −233 mm, and −255 mm, respectively. The findings of this study provide deeper insights into the mechanical behavior of inflatable arch structures under wind and snow loads and can serve as a valuable reference for their design and optimization. Full article

The Chang 7 shale oil reservoirs of the Yanchang Formation in the Heishui Area of the Ordos Basin display typical tight sandstone characteristics, marked by complex microscopic pore structures and limited flow capacity, which severely constrain efficient development. Using a suite of laboratory techniques—including nuclear magnetic resonance, mercury intrusion porosimetry, oil–water relative permeability, spontaneous imbibition experiments, scanning electron microscopy, and thin section analysis—this study systematically characterizes representative tight sandstone samples and examines the microscopic distribution of remaining oil, flow behavior, and their controlling factors. Results indicate that residual oil is mainly stored in nanoscale micropores, whereas movable fluids are predominantly concentrated in medium to large pores. The bimodal or trimodal T₂ spectra reflect the presence of multiscale pore–fracture systems. Spontaneous imbibition and relative permeability experiments reveal low displacement efficiency (average 41.07%), with flow behavior controlled by capillary forces and imbibition rates exhibiting a three-stage pattern. The primary factors influencing movable fluid distribution include mineral composition (quartz, feldspar, lithic fragments), pore–throat structure (pore size, sorting, displacement pressure), physical properties (porosity, permeability), and heterogeneity (fractal dimension). High quartz and illite contents enhance effective flow pathways, whereas lithic fragments and swelling clay minerals significantly impede fluid migration. Overall, this study clarifies the coupled “lithology–pore–flow” control mechanism, providing a theoretical foundation and practical guidance for the fine characterization and efficient development of tight oil reservoirs. The findings can directly guide the optimization of hydraulic fracturing and enhanced oil recovery strategies by identifying high-mobility zones and key mineralogical constraints, enabling targeted stimulation and improved recovery in the Chang 7 and analogous tight reservoirs. Full article

CO₂ miscible flooding provides dual advantages in enhancing oil recovery and facilitating geological sequestration, and has become a key technical approach for developing low-permeability oil reservoirs and carbon emission reduction. The pore-scale flow mechanisms governing CO₂ behavior during miscible flooding are crucial for achieving efficient oil recovery and secure geological storage of CO₂. In this study, pore-scale two-phase flow simulations of CO₂ miscible flooding in porous media are performed using a coupled laminar-flow and diluted-species-transport framework. The model captures the effects of diffusion, concentration distribution, and pore structure on the behavior of CO₂ miscible displacement. The results indicate that: (1) during miscible flooding, CO₂ preferentially displaces oil in larger pore throats and subsequently invades smaller throats, significantly improving the mobilization of oil trapped in small pores; (2) increasing the injection velocity accelerates the displacement front and improves oil utilization in dead-end and trailing regions, but a “velocity saturation effect” is observed—when the inject velocity exceeds 0.02 m/s, the displacement pattern stabilizes and further gains in ultimate recovery become limited; (3) higher injected CO₂ concentration accelerates CO₂ accumulation within the pores, enlarges the miscible sweep area, promotes a more uniform concentration field, leads to a smoother displacement front, and reduces high-gradient regions, thereby suppressing local instabilities, and improves displacement efficiency, although its effect on overall recovery remains modest; (4) CO₂ dynamic viscosity strongly influences flow stability: low-viscosity conditions promote viscous fingering and severe local bypassing, whereas higher viscosity stabilizes flow but increases injection pressure drop and energy consumption, indicating a necessary trade-off between flow stability and operational efficiency. Full article

Free-floating shared e-scooters (FFSE) have been promoted as a sustainable urban mobility solution, yet their true energy and environmental impact remain contested. This study conducts an attributional life cycle assessment (aLCA) across 32 cities in Europe and North America to evaluate the fossil energy consumption and greenhouse gas (GHG) emissions of FFSE systems. By integrating real-world operational data—including vehicle lifespan, daily turnover rates, and city-specific modal substitution patterns—we quantify the direct and net environmental impacts under varying rebalancing and charging scenarios. Results indicate that FFSE systems do not inherently provide net energy and environmental benefits. Instead, achieving net reductions in greenhouse gas emissions and fossil energy consumption depends on systems operating beyond specific thresholds of service life and total travel distance. These thresholds vary dramatically across cities, influenced by modal substitution patterns and local operational efficiency (i.e., rebalancing intensity, daily turnover rates, and trip distance). Cities with high car displacement and efficient operations achieve net GHG and energy savings at lower life cycle mileages, whereas systems that replace walking or public transit often have negative impacts. Additionally, the distribution of energy and environmental impacts across the life cycle shifts fundamentally with vehicle longevity. When the travel distance exceeds 4000–5000 km, it transitions from being manufacturing-dominated to operation-dominated, with rebalancing and electricity use becoming the primary contributors. The research provides evidence-based guidance for policymakers and operators seeking to maximize the contribution of shared micromobility systems to energy conservation and emission reduction. Full article

In the semi-desert aeolian sand areas of Northern China, surface deformation monitoring with SAR is challenged by loss of coherence due to mobile dunes, seasonal vegetation changes, and large-gradient, nonlinear subsidence from underground mining. This study utilizes PALSAR-2 (L-band, 3 m resolution) and Sentinel-1 (C-band, 30 m resolution) data, applying InSAR and Offset tracking methods combined with differential, Stacking, and SBAS techniques to analyze deformation monitoring effectiveness and propose an efficient dynamic monitoring strategy for the Shendong Coalfield. The main conclusions can be summarized as follows: (1) PALSAR-2 data, which has advantages in wavelength and resolution (L-band, multi-look spatial resolution of 3 m), exhibits better interference effects and deformation details compared to Sentinel-1 data (C-band, multi-look spatial resolution of 30 m). The highly sensitive differential-InSAR (D-InSAR) can promptly detect new deformations, while Stacking-InSAR can accurately delineate the range of rock strata movement. SBAS-InSAR can reflect the dynamic growth process of the deformation range as a whole, and SBAS-Offset is suitable for observing the absolute values and morphology of the surface moving basin. The combined application of Stacking-InSAR and Stacking-Offset methods can accurately acquire the three-dimensional deformation field of mining-induced strata movement. (2) The spatiotemporal process of surface deformation caused by coal mining-induced strata movement revealed by InSAR exhibits good correspondence with both the underground mining progress and the development of ground fissures identified in UAV images. (3) The maximum displacement along the line of sight (LOS) measured in the mining area is approximately 2 to 3 m, which is close to the 2.14 m observed on site and aligns with previous studies. The calculated advance influence angle of the No. 22308 working face in the study area is about 38.3°. The influence angle on the solid coal side is 49°, while that on the goaf side approaches 90°. These findings further deepen the understanding of rock movement and surface displacement parameters in this region. The dynamic monitoring strategy proposed in this study is cost-effective and operational, enhancing the observational effectiveness of InSAR technology for surface deformation due to coal mining in this area, and it enriches the understanding of surface strata movement patterns and parameters in this region. Full article