Search Results (1,266)

With the rapid development of e-commerce, logistics UAVs (unmanned aerial vehicles) have shown great potential in the field of urban logistics. However, the large-scale operation of logistics UAVs has brought challenges to air traffic management, and the competitiveness of UAV logistics is still weak compared with traditional ground logistics. Therefore, this paper constructs a double-layer route network structure that separates logistics transshipment from terminal delivery. In the delivery layer, a door-to-door distribution mode is adopted, and the transshipment node service location model is constructed, so as to obtain the location of the transshipment node and the service relationship. In the transshipment layer, the index of the route betweenness standard deviation (BSD) is introduced to construct the route network planning model. In order to solve the above model, a double-layer algorithm was designed. In the upper layer, the multi-objective simulated annealing algorithm (MOSA) is used to solve the transshipment node service location issue, and in the lower layer, the multi-objective non-dominated sorting genetic algorithm II (NSGA-II) is adopted to solve the network planning model. Based on real obstacle data and the demand situation, the double-layer network was constructed through simulation experiments. To verify the network rationality, actual flights were carried out on some routes, and it was found that the gap between the UAV’s autonomous flight route time and the theoretical calculations was relatively small. The simulation results show that compared with the single-layer network, the total distance with the double-layer network was reduced by 62.5% and the structural intersection was reduced by 96.9%. Compared with the minimum spanning tree (MST) algorithm, the total task flight distance obtained with the NSGA-II was reduced by 42.4%. The BSD factors can mitigate potential congestion risks. The route network proposed in this paper can effectively reduce the number of intersections and make the UAV passing volume more balanced. Full article

Differences in male (M) and female (F) neonates’ premature birth outcomes and placental trophoblast inflammation have been observed but are unknown to occur within the fetal membrane trophoblast layer (chorion trophoblasts [CTC]). This study examined whether sex-based differences in gene expression and inflammatory marker expression can be observed in CTCs under control or infectious inflammatory conditions modeling preterm birth. CTCs from six different patient-derived fetal membrane samples (3M/3F) were cultured and divided into experimental (Lipopolysaccharide [LPS]) and control groups for 6, 12, or 24 h. RNA from CTCs was subjected to RNA-seq, while cytokine multiplex or ELISA detected pro-/anti-inflammatory cytokines, progesterone, and soluble HLA-G in cell supernatants. CTC-M and CTC-F showed sex, time, and stimulant-dependent differential gene expression profiles. Cytokine analysis demonstrated a significantly lower IL-6 production in control CTC-M than in CTC-F. No sex-dependent responses were observed after LPS treatment regarding cytokines. CTC-M produced significantly lower progesterone than CTC-F. The theories of sexual dimorphism linked to placental inflammation may not extend to CTCs. This study supports that the chorion acts as a “great wall” protecting the fetus by being refractory to insults. Further examination into the weaknesses of the chorion barrier and sex-dependent responses of fetal membranes is needed. Full article

Industrialization trial production of high permeability (Hi-B) steel was carried out by “one cold rolled + decarburization and nitridation technologies”. The finished product reached the level of 23Q100 with an average grain size of 5.47 cm, magnetic flux density B₈ of 1.902T, and the iron loss P_1.7/50 of 0.975 W/Kg. The evolution law of the microstructure and texture under different processes was analyzed with the help of OM, EBSD, and XRD. The results showed that the microstructure of the hot rolled plate was equiaxed crystals in the surface layer, a mixture of recrystallization grains and banded fiber in the quarter of the thickness layer, and banded fiber in the center layer. The texture gradient of the hot rolled plate from the surface layer to the center layer was {112}<111> + {110}<114> → {441}<014> → {001}~{111}<110>. The texture of the normalized plate was in major {110}<113> in the surface layer, diffuse α-fiber texture and {441}<014> in the quarter of the thickness layer, and sharp α texture {001}~{111}<110> in the center layer. The texture of the cold-rolled sheet was concentrated in {001}~{332}<110>. The average grain size of the decarburizing and nitriding sheet was 26.4 μm, and the texture of the first recrystallization is sharp α*-fiber and weak {111}<112>. The finished product has a sharp single Goss texture. For Hi-B steel, the Goss secondary nucleus originated from the surface layer to 1/4 layer of the hot rolled plate and reached the highest content of 11.5% in the quarter of the thickness. The content of the Goss texture decreased with the subsequent normalization and cold rolling, then the Goss grains nucleated again during the decarburization annealing and high temperature annealing processes. Full article

This study investigates the scale effects on the experimental shear strength of earthen walls, a critical parameter influencing the seismic performance of adobe and rammed-earth (RE) buildings. Recognized for their historical significance and sustainable construction practices, earthen structures require a comprehensive understanding of their mechanical behavior under shear loads to ensure effective design and preservation. This research compiles data from over 120 in-plane shear wall tests (adobe and RE), nearly 20 direct shear tests from the scientific and technical literature, and new cyclic direct shear tests performed on large cubic specimens (300 mm side length) made from the same material as a previously tested two-story RE wall. Based on the findings, this study recommends a minimum specimen cross-sectional area of 0.5 m² for reliable shear strength testing of earthen walls in structural laboratories. This recommendation aims to prevent the unconservative overestimation of shear strength commonly observed in smaller specimens, including direct shear tests. Furthermore, the Mohr–Coulomb failure criterion outlined in the AIS-610 Colombian standard is validated as a conservative lower bound for all compiled shear strength data. Cyclic direct shear tests on nine 300 mm cubic specimens produced a Mohr–Coulomb envelope with an apparent cohesion of 0.0715 MPa and a slope of 0.66, whereas the full-scale two-story wall (5.95 × 6.20 × 0.65 m) constructed with the same material exhibited a much lower cohesion of 0.0139 MPa and a slope of 0.26. The analysis reveals significant scale effects, as small-scale specimens consistently overestimate shear strength due to their inability to capture macro-structural behaviors such as compaction layer interactions, construction joint weaknesses, and stress redistributions. Based on the analysis of the compiled data, the novelty of this study lies in defining a strength reduction factor for direct shear tests (3.4–3.8 for rammed earth, ~3.0 for adobe) to align with full-scale wall behavior, as well as establishing a minimum specimen size (≥0.5 m²) for reliable in-plane shear testing of earthen walls, ensuring accurate structural assessments of shear strength. This study provides a first approach to the shear behavior of unstabilized earth. To expand its application, future research should explore how the scale of specimens with different stabilizers affects their shear strength. Full article

Tapered piles are a new type of pile foundation known for their simple construction and high bearing capacity, commonly used in railway, highway, or building foundation treatment. This study proposes a unified dynamic Winkler model for vertical and lateral vibration response of tapered piles in the frequency domain using the impedance function transfer matrix method. The computational expressions are obtained for the different springs and damping of tapered piles with different dimensions using the elastodynamic theoretical of rigid embedded foundations, and the dynamic interaction mechanisms of vertical and lateral vibrations between tapered piles and soil are analyzed. The rationality of the simplified model is validated by comparison with existing literature and finite element simulation results. Finally, an example is provided to discuss the influences of the dimensional parameters of the pile and soil properties on vertical, lateral, and rocking dynamic impedance. The analytical findings demonstrate that the lateral and rocking dynamic impedances of tapered piles undergo a substantially greater enhancement relative to their vertical counterpart as the taper angle is progressively enlarged, assuming the pile volume remains constant. The dynamic impedance of tapered piles under vertical and lateral vibration in upper hard and lower weak soil layers, or upper weak and lower hard soil layers, are both greater than those in a homogeneous foundation. Specifically, the vertical dynamic stiffness of tapered piles in double-layered soils is approximately twice that of homogeneous soil. The rocking dynamic stiffness of the pile is significantly influenced by the soil properties around the pile foundation, whereas the soil properties have little impact on the rocking damping coefficient. Overall, the vertical dynamic characteristics are less influenced by the geometric features of the upper part of the tapered pile, while the lateral dynamic characteristics are significantly affected by these features. The lateral dynamic impedance of the tapered pile increases with the diameter of the upper part of the pile. Furthermore, the vertical, lateral, and rocking dynamic impedance of the pile can be effectively improved by enhancing the soil properties around its upper section. These results can provide theoretical references for the engineering practice. Full article

Open-pit mining often exposes weak rock layers, the strength of which significantly affects the stability of slopes. If these rock layers are also prone to disintegration and expansion, cyclic rainfall can exacerbate instability. Rainfall-induced changes in the seepage field also indirectly threaten the stability of slopes. Therefore, investigating the characteristics of mudstone limestone and the impact of the seepage field on slope instability under different wet–dry cycles is of great significance for the safe mining of open-pit mines. This paper takes the mudstone limestone slope of a certain open-pit mine in the southwest as the starting point and conducts experiments on saturated density, water absorption rate, permeability coefficient, compressive strength, and variable angle shear strength. Combined with scanning electron microscopy and phase analysis of X-ray diffraction analysis, the macroscopic and microscopic characteristics of the samples are comprehensively analyzed. FLAC3D software is used to explore the changes in the seepage field and the mechanism of instability. Our research found that for the preparation of mudstone limestone samples, a particle size of less than 1 mm and a drying temperature of 50 °C are optimal, with specific values for initial natural and saturated density, and natural water content. As the number of wet–dry cycles increases, the saturated density of mudstone limestone increases; the water absorption rate first rises sharply and then rises slowly; the permeability coefficient first rises sharply and then stabilizes, finally dropping sharply; the compressive and shear strength decreases slowly, and the internal friction angle changes little; frequent cycles also lead to mudification and seepage filtration. At the microscopic level, pores become larger and more regular, and the distribution is more concentrated; changes in mineral content weaken the strength. Combined with numerical simulation, the changes in the seepage field at the bottom of the slope exceed those at the slope surface and top, the transient saturated area expands, and the overall and local slope stability coefficients gradually decrease. During the third cycle, the local stability is lower than the overall stability, and the landslide trend shifts. In conclusion, wet–dry cycles change the pores and mineral content, affecting the physical and mechanical properties, leading to the deterioration of the transient saturated area, a decrease in matrix suction, and an increase in surface gravity, eventually causing slope instability. Full article

For the new type of CFRP (Carbon Fiber Reinforced Plastic) thin-walled components with a large size and weak rigid structure, due to the integration of geometric features and the reduction in the amount of parts, the assembly size transmission chain is short compared to traditional metal assembly structures. In addition, the manufacturing errors and layer parameters of large composite parts in different regions are different, and they also have a lower forming accuracy. For the current assembly method that mainly concerns geometric dimensions and tolerances, it is difficult to support precise analysis and accurate geometric error forms for different local and global regions. As a result, in practical engineering, the forced method of applying a local clamping force is inevitably adopted to passively reduce and compensate for assembly errors. However, uneven stress distribution and possible internal damage occur. To avoid the assembly quality problems caused by forced clamping operations, the research status on the optimization of forced clamping process parameters before assembly, the flexible position–force adjustment of fixtures during assembly, and gap compensation and strengthening before assembly completion was analyzed systematically. The relevant key technologies, such as force limit setting, geometric gap reduction, stress/damage evolution prediction, the reverse optimization of clamping process parameters, and precise stress/damage measurement, are proposed and resolved in this paper. With the specific implementation solutions, geometric and mechanical assembly status coupling analysis, active control, and a collaborative guarantee could be achieved. Finally, future research work is proposed, i.e., dynamic evolution behavior modeling and the equalization of the induction and control of physical assembly states. Full article

Fluid dynamic noise produced by eddy disturbances and friction along pipe walls poses a significant challenge in natural gas transmission and distribution stations. (K)TS control valves are widely used in natural gas transmission and distribution stations across Southwest China and are among the primary sources of noise in these facilities. In this study, a 3D geometric model of the (K)TS valve was developed, and the gas flow characteristics were simulated to analyze the gas flow field and sound field within the valve under varying pipeline flow velocities, outlet pressures, and valve openings. The results demonstrate that accurate calculations of the 3D valve model can be achieved with a grid cell size of 3.6 mm and a boundary layer set to 3. The noise-generating regions of the valve are concentrated around the throttle port, valve chamber, and valve inlet. The primary factors contributing to the aerodynamic noise include high gas flow velocity gradients, intense turbulence, rapid turbulent energy dissipation, and vortex formation and shedding within the valve. An increase in inlet flow velocity intensifies turbulence and energy dissipation inside the valve, while valve opening primarily influences the size of vortex rings in the valve chamber and throttle outlet. In contrast, outlet pressure exerts a relatively weak effect on the flow field characteristics within the valve. Under varying operating conditions, the noise directivity distribution remains consistent, exhibiting symmetrical patterns along the central axis of the flow channel and forming six-leaf or four-leaf flower shapes. As the distance from the monitoring point to the valve increases, noise propagation becomes more concentrated in the vertical direction of the valve. These findings provide a theoretical basis for understanding the mechanisms of aerodynamic noise generation within (K)TS control valves during natural gas transmission, and can also offer guidance for designing noise reduction solutions for valves. Full article

Offshore multilayer sandstone reservoirs are characterized by complex vertical alternating thick and thin layers, resulting in significant heterogeneity. Traditional productivity evaluation methods often fail to effectively represent the dynamic production patterns of individual wells. This study focuses on the S oilfield offshore (Bohai Bay, China) as a case study. By considering the structural characteristics of thin layers and sand bodies, the reservoir is classified into four types: strong continuous thick layers, weak continuous thick layers, alternating thick–thin layers, and weak continuous thin layers. Based on this classification, a multilayer perceptron classification model based on graph attention neural networks is developed. The model achieves a high classification accuracy of 96.6% by mining the interdependencies between 14 input parameters. Further, by fitting the relationship between interlayer interference coefficients and water cuts for typical wells, a dynamic variation diagnosis plot for interlayer interference coefficients under different reservoir combinations is established. Additionally, a calculation method for the oil productivity index based on reservoir combination patterns is proposed. The method’s effectiveness was validated through field application, where the results significantly improved the correlation between the water-free oil productivity index and flow coefficient, with calculation errors of less than 10% compared to measured values. Full article

Membrane technology has been widely used in industrial CO₂ capturing, gas purification and gas separation, arousing attention due to its advantages of high efficiency, energy saving and environmental protection. In the context of reducing global carbon emissions and combating climate change, it is particularly important to capture and separate greenhouse gasses such as CO₂. Zr-MOF can be used as a multi-dimensional modification on the polymer membrane to prepare self-assembled MOF-based mixed matrix membranes (MMMs), aiming at the problem of weak adhesion or bonding force between the separation layer and the porous carrier. When defective UiO-66 is applied to PVDF membrane as a functional layer, the CO₂ separation performance of the PVDF membrane is significantly improved. TUT-UiO-3-TTN@PVDF has a CO₂ permeation flux of 14,294 GPU and a selectivity of 27 for CO₂/N₂ and 18 for CO₂/CH₄, respectively. The CO₂ permeability and selectivity of the membrane exhibited change after 40 h of continuous operation, significantly improving the gas separation performance and showing exceptional stability for large-scale applications. Full article

Finding a template location in a query image is a fundamental problem in many computer vision applications, such as localization of known objects, image registration, image matching, and object tracking. Currently available methods fail when insufficient training data are available or big variations in the textures, different modalities, and weak visual features exist in the images, leading to limited applications on real-world tasks. We introduce Self-Supervised Foundation Model for Template Matching (Self-TM), a novel end-to-end approach to self-supervised learning template matching. The idea behind Self-TM is to learn hierarchical features incorporating localization properties from images without any annotations. As going deeper in the convolutional neural network (CNN) layers, their filters begin to react to more complex structures and their receptive fields increase. This leads to loss of localization information in contrast to the early layers. The hierarchical propagation of the last layers back to the first layer results in precise template localization. Due to its zero-shot generalization capabilities on tasks such as image retrieval, dense template matching, and sparse image matching, our pre-trained model can be classified as a foundation one. Full article

This paper presents the results of the analysis of the redistribution of cesium-137 (¹³⁷Cs) in the bottom sediments of beaver ponds in two small rivers in the forest-steppe north of the Volga Upland, which is one of the most contaminated areas of the Middle Volga region (European Russia) with artificial radionuclides. This study is based on fieldwork materials, laboratory analyses of the specific radioactivity of ¹³⁷Cs in soil and bottom sediment samples, their granulometric composition, and the content of organic matter in them. The obtained results indicate a significant decrease in the specific activity of ¹³⁷Cs in the direction from near-water-divide surface soils (on average, 54 Bq/kg) to the bottom sediments of beaver ponds of the studied rivers (on average, no more than 6 Bq/kg). A weak (statistically insignificant) tendency towards a decrease in the specific activity of ¹³⁷Cs in the bottom sediments of beaver ponds downstream of rivers was also revealed. With this detected trend, no statistically significant relationship was found between changes in ¹³⁷Cs and changes in the granulometric composition of bottom sediments. However, a relatively good relationship was identified with changes in the content of total organic matter. The stage-by-stage accumulation of sediment thickness in one of the beaver ponds was revealed, with the highest concentration of ¹³⁷Cs in the layer with the highest content of finely dispersed fractions and organic matter. The obtained results indicate that for a correct quantitative assessment of the migration of pollutants (including radioactive ones) in floodplain-channel systems, it is necessary to consider beaver structures (primarily ponds), which act as zones of their intensive accumulation. Full article

Background/Objectives: An assessment of the retinal image quality in adaptive optics optical coherence tomography (AO-OCT) is challenging. Many factors influence AO-OCT imaging performance, leading to greatly varying imaging results, even in the same subject. The aim of this study is to introduce quantitative means for an assessment of AO-OCT image quality and to compare these with parameters retrieved from the pyramid wavefront sensor of the system. Methods: We used a spectral domain AO-OCT instrument to repetitively image six patients suffering from diabetic retinopathy over a time span of one year. The data evaluation consists of two volume acquisitions with a focus on the photoreceptor layer, each at five different retinal locations per visit; 7–8 visits per patient are included in this data analysis, resulting in a total of ~420 volumes. Results: A large variability in AO-OCT image quality is observed between subjects and between visits of the same subject. On average, the image quality does not depend on the measurement location. The data show a moderate correlation between the axial position of the volume recording and image quality. The correlation between pupil size and AO-OCT image quality is not linear. A weak correlation is found between the signal-to-noise ratio of the wavefront sensor image and the image quality. Conclusions: The introduced AO-OCT image quality metric gives useful insights into the performance of such a system. A longitudinal assessment of this metric, together with wavefront sensor data, is essential to identify factors influencing image quality and, in the next step, to optimize the performance of AO-OCT systems. Full article

The Mahu Sag, where the Mahu 1 well block is located, is one of the most important hydrocarbon-rich depressions in the Junggar Basin, NW China. The Permian Upper Wuerhe Formation (UWF) constitutes the primary layer of the unconventional tight oil reservoir in the Mahu Oilfield. To explore the provenance and sedimentary environment during the deposition of the UWF in the study area, we determined the clay mineralogy and whole-rock geochemical composition of argillaceous rocks. The results show that the primary minerals in argillaceous rock are feldspar, clay minerals, quartz, and a minor amount of hematite. The clay minerals identified included illite, smectite, kaolinite, chlorite, and illite/smectite mixed layers. The tectonic setting of the provenance area for the UWF is a continental island arc, associated with a cutting magmatic arc. The main provenance area is related to the Baogutu tectonic belt (the Zhayier Mountain and the Hala’alate Mountain). The bedrock primarily consists of acidic igneous rocks, with minor occurrences of intermediate–basic igneous and sedimentary rock. The chemical index of alteration (CIA) shows that the parent rocks of the argillaceous rocks have experienced moderate–strong chemical weathering. Combining the Sr/Cu and ΣLREE/ΣHREE ratios, δEu values, and clay mineral characteristics, we determined that the paleoclimate during the deposition of the UWF was generally warm and humid, with occasional short-term dry and cold periods. The UWF gradually changes, according to the relative humidity and enhanced chemical weathering from the bottom to the top. An analysis of trace elements, paleosalinity, and paleowater depth indicate that the studied argillaceous rocks were deposited in a shallow-water oxidation environment of continental fresh water with weak hydrodynamic conditions. Full article

This study investigates the fresh state and hardened state mechanical and durability properties of 3D-printed concrete. The mechanical tests focused on its anisotropic behavior in response to different load orientations. Compressive, flexural, and splitting tensile strengths were evaluated relative to the print layers orientation. Results showed that compressive strength varied significantly, achieving 85% of cast sample strength when the load was applied parallel to the print layers ([u] direction), 71% when the load was applied perpendicular to the print object’s side plane ([v] direction), while only reaching 59% when applied perpendicular to the top plane ([w] direction). Similar trends were observed for flexural strength, with average values reaching 75% of cast sample strength when the load was applied perpendicular to the print layers ([v.u] and [w.u] directions), but decreasing to 53% when the load was applied parallel to print layers ([u.w] direction), underscoring the weaknesses at interlayer interfaces. The splitting tensile strength remained relatively consistent across print orientations, reaching 90% of the cast sample strength. Durability assessment tests revealed that 3D-printed concrete exhibits reduced resistance to environmental factors, particularly at the layer interfaces where the cold joint was formed, which are prone to moisture penetration and crack formation. These findings contribute valuable insights into the mechanical and durability properties of 3D-printed concrete, emphasizing the importance of print orientation and interlayer bonding in its performance. This understanding helps guide the optimal use of 3D-printed elements in real-life applications by aligning load or exposure to environmental factors with the material’s strength and durability characteristics. Full article