Search Results (32)

The lower melt strength of biodegradable materials in comparison to low density polyethylenes raises serious issues regarding their processability via blown film molding. Thus, reliable rheological characterization is a viable option for assessing their efficient flow performance. The blends of poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) modified with four chain-extending cross-linkers (CECLs) undergo shearing during extrusion and are subjected to extensional deformation during the subsequent film blowing. The shear viscosity data obtained with a capillary rheometer corresponded well to the molecular weights obtained by gel permeation chromatography, while an evaluation of elongational viscosity using a Sentmanat Extensional Rheometer failed due to sample sagging during the process of temperature setting and an unacceptable deviation from the theoretically supposed exponential decrease of sample cross-sections. Therefore, the response of the PBAT/PLA blends to elongation was determined via changes in the duration of time intervals corresponding to the rupture of elongated samples. An increased consistency of the PBAT/PLA blends with CECL, as previously indicated by dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy, was evaluated in this way. Full article

The Shahejie Formation in Nanpu Sag is a crucial region for deep-layer hydrocarbon exploration in the Bohai Bay Basin. To address the impact of faults on sublacustrine fan formation and spatial distribution within the study area, this study integrated well logging, laboratory analysis, and 3D seismic data to systematically analyze sedimentary characteristics of sandbodies from the first member of the Shahejie Formation (Es₁) sublacustrine fans, clarifying their planar and cross-sectional distributions. Further research indicates that Gaoliu Fault activity during Es₁ deposition played a significant role in fan development through two mechanisms: (1) vertical displacement between hanging wall and footwall reshaped local paleogeomorphology; (2) tectonic stresses generated by fault movement affected slope stability, triggering gravitational mass transport processes that remobilized fan delta sediments into the central depression zone as sublacustrine fans through slumping and collapse mechanisms. Core observations reveal soft-sediment deformation features, including slump structures, flame structures, and shale rip-up clasts. Seismic profiles show lens-shaped geometries with thick centers thinning laterally, exhibiting lateral pinch-out terminations. Inverse fault-step architectures formed by underlying faults control sandbody distribution patterns, restricting primary deposition locations for sublacustrine fan development. The study demonstrates that sublacustrine fans in the study area are formed by gravity flow processes. A new model was established, illustrating the combined control of the Gaoliu Fault and reverse stepover faults on fan development. These findings provide valuable insights for gravity flow exploration and reservoir prediction in the Nanpu Sag, offering important implications for hydrocarbon exploration in similar lacustrine rift basins. Full article

This study focuses on the clastic reservoir in the first member of Yaojia Formation within Qijia-Gulong Sag, Songliao Basin. The results indicate that the reservoir in the study area develops within a shallow-water delta sedimentary system. The dominant sedimentary microfacies comprise underwater distributary channels, mouth bars, and sheet sands. Among these, the underwater distributary channel microfacies exhibits primary porosity ranging from 15.97% to 17.71%, showing the optimal reservoir quality, whereas the sheet sand microfacies has a porosity of only 7.45% to 12.08%, indicating inferior physical properties. During diagenesis, compaction notably decreases primary porosity via particle rearrangement and elastic deformation, while calcite cementation and quartz overgrowth further occlude pore throats. Although dissolution can generate secondary porosity (locally up to 40%), the precipitation of clay minerals tends to block pore throats, leading to “ineffective porosity” (permeability generally < 5 mD) and overall low-porosity and low-permeability characteristics. Carbon–oxygen isotope analysis reveals a deficiency in organic acid supply in the study area, restricting the intensity of dissolution alteration. Reservoir quality evolution is dominantly governed by the combined controls of sedimentary microfacies and diagenesis. This study emphasizes that, within shallow-water delta sedimentary settings, the material composition of sedimentary microfacies and the dynamic equilibrium of diagenetic processes jointly govern reservoir property variations. This insight provides critical theoretical support for understanding diagenetic evolution mechanisms in clastic reservoirs and enabling precise prediction of high-quality reservoir distribution. Full article

Background/Objectives: The preschool period plays an essential role in shaping a child’s overall development, which influences physical, emotional, social, and cognitive growth. At this stage, establishing proper postural habits is essential, as it can have lasting effects on health, well-being, helps to prevent future issues, and supports overall development. Therefore, the present work aims to determine the differences in postural status between boys and girls of preschool age. Methods: The sample of participants consisted of 92 children (n = 46 boys and n = 46 girls); the average age for girls was 5.41 ± 0.30 years and for boys it was 5.53 ± 0.31 years. Data were collected using licensed state-of-the-art diagnostic equipment, Contemplas 3D Posture Compact, using 16 variables to assess postural status with a Mann–Whitney U test. Results: The results of this study indicate that boys have more pronounced deformities in the following variables: shoulder displacement (p = 0.047), pelvic obliquity (p = 0.000), sag. distance cervical spine–sacrum (p = 0.029), sag. distance thoracic spine–sacrum (SDTS) (p = 0.016), and sag. distance lumbar spine–sacrum (SDLS) (p = 0.005). Conclusions: This study confirmed gender differences in postural characteristics in preschool children. Boys showed a greater tendency towards postural deviations, indicating the necessity for specific interventions and programs to improve their posture. On the basis of the results of this research, it is recommended to carry out cross-cultural research that would enable the comparison of results among children from different environments and cultural contexts in order to determine possible differences and particularities in the development of postural characteristics. Future research should include larger and more diverse samples of participants, including children from rural and urban areas, in order to ensure the representativeness and generalizability of the results. In addition, conducting a longitudinal study that would monitor the postural characteristics of children through different developmental stages is suggested, aiming to identify critical periods for intervention and to determine, more precisely, development trends within the context of gender differences. Full article

Double-layer pipelines are widely used in deep-sea energy transport because of their strong thermal insulation and enhanced structural safety. The stress distribution and the interaction mechanism between inter-pipes of double-layer pipelines are elucidated. A mechanical model is developed to characterize the thermal deformation difference between the two layers. The mechanical response of the pipeline can be divided into two distinct modes based on the initial deformation stages: (1) an inner-pipe-dominated elongation that creates compressive stress in the inner pipe and tensile stress in the outer pipe, and (2) an outer-pipe-dominated elongation that reverses this stress distribution. Sagging deformation (bowl-shaped deformation), primarily caused by the self-weight of the inner pipe, is identified as the critical factor that drives the stress concentration and bending moment at the inner–outer pipe connection. Engineering approaches, such as inserting spacers or additional supports in the annular cavity, effectively reduce peak stresses in both layers under extreme conditions. Full article

The quest for surgical advancements regarding the enhancement of the submental and cervicofacial regions has witnessed a remarkable upsurge in recent years. Informed patients are actively seeking sophisticated plastic surgery techniques to achieve comprehensive rejuvenation in these specific areas. Common complaints expressed by these patients include sagging of the jawline, the emergence of deep perioral wrinkles, and the formation of “marionette lines” within the lower third of the face. Furthermore, the manifestation of age-related signs, including neck laxity, submental adipose accumulation, “witch’s chin” deformity, and weakened platysma musculature, are common within this anatomical region. This literature review aims to summarize recent technical improvements, historical evolution, indications, postoperative care, and challenges for facial rejuvenation of the lower third of the face and neck. The application of minimally invasive procedures as part of a comprehensive approach for an aging face will also be discussed. In this article, an extensive search of the available literature was conducted using leading databases, including PubMed and MEDLINE, with the keywords “neck lift”, “platysmaplasty”, “facial rejuvenation”, “medial platysmaplasty”, “lateral platysmaplasty”, “neck rejuvenation”, and “cervicofacial rejuvenation”. Full article

This study analyzes the results of a displacement measurement of the Sungnyemun Gate’s structural members, such as column, girder, and hip rafter, carried out by the National Institute of Cultural Heritage for about 10 years from December 2013 to October 2022. Through this, we attempt to examine the behavior of wooden architectural heritage sites according to seasonal changes and infer the factors influencing structural deformation. As a result of the analysis, it was confirmed that the structural members of the Sungnyemun Gate, including the columns, girders, and hip rafters, continued to move and that the displacement of members was accumulated, and the structure was deformed. It was also confirmed that member displacements accumulated in a specific direction. In the case of the Sungnyemun Gate, the column leaning south, the hip rafters’ endpoint sagging, and the girders’ center deflecting were continuously observed. Furthermore, the behavior of wooden architectural heritage sites, where displacement accumulates as it undergoes repeated deformation and recovery according to seasonal changes, was also revealed in detail. The deformation of the Sungnyemun Gate’s members shows a pattern that reflects the mechanical properties of wood, which repeatedly increases and decreases displacement depending on the season. However, seasonal deformation did not appear the same in all the members. Even the same member has an uneven drying speed due to differences in the amount of sunlight it receives depending on its location, which leads to uneven distribution of deformation. The significance of this study is that it examined the behavior of a wooden architectural heritage site in detail based on the quantitative results of long-term measurements and prepared primary data for the future management of wooden architectural heritage sites. Full article

Nanocomposite flexible polyurethane foams (nFPUfs) were obtained by modifying the polyurethane formulation by adding a halloysite nano-filler in the amount of one to five parts by weight per hundred parts of used polyol (php). Flexible polyurethane (PU) foams with an open-cell structure and with a beneficial SAG factor were obtained. Premixes with nano-filler had a lower reactivity than the reference PU system. This favored the production of smaller cells, but with a more rounded shape in comparison with the REF foam without the nano-filler. During the study, the morphology and physical and mechanical properties were characterized, including apparent density, compressive stress, rebound flexibility, SAG factor, closed-cell content, and thermal stability, and compared with the properties of the unmodified reference foam. Scanning electron microscopy (SEM) showed that the cell structures of all prepared foams were open, and the cell size decreased with increasing nano-filler content. Apparent densities, SAG factors and rebound flexibilities of the foams increased with the increase of nano-filler content, while the resistance to permanent deformation showed the opposite trend. The proper selection of raw materials and optimally developed polyurethane formulations allow for obtaining environmentally friendly foams with favorable functional properties, taking into account price and the needs of sustainable development in the synthesis of flexible foams dedicated to the upholstery industry. Full article

This study addresses the issue of unsatisfactory smoothness in the movement of integrated internal and external cross roller bearings post-assembly, which compromises the movement flexibility of the finished bearing and fails to meet index requirements. Focusing on a specific type of precision cross roller bearing, this paper establishes a finite element explicit dynamic simulation model that takes into account the plugging position and matching relationship. A transient dynamic simulation of the roller blockage process was conducted, yielding insights into the contact pressure and deformation experienced by the roller and plug during this blockage. The results indicate that when both the taper pin are positioned centrally, and the plug matching clearance, plug sag and protruding amount, and plug rotation offset degrees are all set to 0 μm, the contact pressure between the roller and raceway, as well as the roller deformation displacement, are minimized. The plugging position and fit were subsequently validated through testing, which also measured the impact of these parameters on the roundness of the raceway surface and the bearing’s friction torque. The test findings corroborate that when the taper and pin are centrally aligned, and the stopper clearance is 5 μm, with the plug sag, protrusion, and offset all at 0 μm, the roundness of the raceway surface and the bearing’s friction torque reach their lowest values, thereby optimizing the stability of bearing motion. By comparing the simulation and experimental results, it is concluded that during bearing assembly, it is crucial to maintain the taper pin in a central position, control the plug matching clearance to approximately 5 μm, and ensure the plug sag, protrusion, and rotation offset amount are both at 0 μm. This approach guarantees optimal contact conditions and motion stability during operation. The findings of this research offer valuable design guidance for the selection of appropriate plugging positions and fits in precision cross roller bearings. Full article

Suspension bridges, such as stress-ribbon, are among the simplest structural bridge systems and have the lowest structural height. The flexibility of these elegant bridges poses great challenges for designers to minimize their deformability under asymmetrical operational loads. Due to the small initial sag, such load-bearing structures also cause significant tensile forces, which requires them to have large cross-sections and massive anchor foundations. This paper analyzes an innovative suspension steel bridge structure combined with a string and a cable. More attention is paid to asymmetric loading as this is more relevant for suspension structures. The new structure is studied numerically and experimentally. It is established that the string stabilizes the displacements of the bridge under asymmetric loading. The stabilization efficiency is proportional to the value of the pre-tension force of the string. The obtained results reveal the behavior of the structure and enable an evaluation of the accuracy of the numerical results, as well as the applied modeling. In addition, the experimentally obtained results allow the evaluation of more aspects of the behavior of the new bridge, which will be useful in further studies of this type of structures. Full article

The mechanical response and deformation characteristics in calcareous sand foundations during pile driving and setup were studied using model tests combined with the technical methods of tactile pressure sensors and close-range photogrammetry. Different types of piles were considered, including a pipe pile, square pile and semi-closed steel pipe pile. The test results show that during pile driving, the pile tip resistance of different piles increases with an increase in the pile insertion depth, and an obvious fluctuation is also obtained due to the particle breakage of the calcareous sand and energy dissipation. Different degrees of particle breakage generated by different type piles make the internal stress variations different, as with the pile tip resistance. The pile tip resistance of model pile A, which simulates a pipe pile, is the highest, followed by model pile B, the simulated square pile. Model pile C, which simulates a semi-closed steel pipe pile, has the smallest pile tip resistance because its particle breakage is the most obvious and the pile tip energy cannot be continuously accumulated. The induced deformation such as sag or uplift on the surface and the associated influence range for the calcareous sand foundation are the smallest for model pile C, followed by model pile B and then model pile A. Model pile A has the most obvious pile driving effect. During the pile setup process after piling, the increase in the total internal stress of model pile B is the largest, and the improvement of the potential bearing capacity is the most obvious, followed by model pile A and model pile C. During the pile setup, the induced uplift deformation in pile driving is recovered and the potential bearing capacity increases due the redistribution and uniformity of the vertical and radial stress distributions in the calcareous sand foundation. Considering the potential bearing capacity of different model piles, the influence range of pile driving, foundation deformation and the pile setup effect, it is suggested to use a pointed square pile corresponding to model pile B in pile engineering in calcareous sand foundations. Full article

This study focuses on thick top foil bearings (TTFBs), which can prevent top foil from sagging and significantly reduce the load capacity of gas foil bearings (GFBs). However, the limited research on the dynamic responses of TTFB-rotor systems has hindered their wide application of TTFBs with high load capacity. To address this, an integrated nonlinear dynamic model is developed to analyze the linear dynamic responses of a rigid rotor supported on TTFBs. The model incorporates time domain orbit simulation, considering unsteady Reynolds equations, foil deformation equations, thick top foil motion equations, and rotor motion equations. A symmetrical test rig is used to validate the model, and three types of TTFBs with different bump foil stiffness are tested, with experimental results aligning with the model predictions. This study also investigates the effects of nominal clearance, static load, and unbalance on TTFB-rotor systems. The results indicate that unbalance has minimal impact on subsynchronous vibrations. However, larger bump foil stiffness, increased normal clearance, and higher static load contribute to improved stability and higher maximum stable speed of the TTFB-rotor system. Moreover, other relevant parameters reducing the bearing attitude angle can further enhance the system’s stability. Full article

In order to study the influence of tunnel volume loss on adjacent framed buildings with different shallow foundations, this paper carried out physical model experiments with two common types of footings (isolated and strip footings) under different working conditions based on the digital image correlation (DIC) technique. The main finding of the present paper is that the increase in formation loss rate will aggravate the deformation and damage of the structure, and the strip foundation shows stronger integrity and stability compared with the isolated foundation in this process. With the increase in the eccentricity of the frames with respect to the tunnel, the overall tilt and damage degree of structural elements increases first and then decreases for both foundations, reaching the maximum value with the eccentric distance of one multiple of the tunnel diameter. Interestingly, when the isolated footings are located directly above the tunnel, the damage in the inner panels is the most severe and gradually decreases with eccentricity, changing from a sagging mode to a hogging mode for the frame form. While the strip footings always maintain slight hogging, and the trend of the damage degree of panels is similar to that of elements, with the eccentric distance reaching two times the tunnel diameter, the strip foundation structure tends to be stable, while the isolated one still needs attention for its potential possibility of damage in panels. The research results have reference value for the impact assessment of adjacent shallow-foundation framed buildings in subway tunnel construction. Full article

Historical buildings have inhabited every epoch of history. Some of these built legacies are now in ruins and dying whilst others are somewhat undamaged. Knowledge of conservation techniques available today has allowed us to understand more innovative ways of conserving the built heritage. Such techniques are, however, incompatible with the building materials available in our historical epoch and environment. People seek to reclaim the forgotten cultural heritage in the midst of the heritage conservation era while bearing in mind that previous work seldom takes into account the inventive preservation methods of today. This study aims to explore the innovative built heritage conservation practice in the Kano metropolis, to detect deterioration and incorporate traditional wisdom and contemporary innovation according to modern urban development. The study adopted qualitative research with a descriptive approach. The descriptive research explains, examines, and interprets prevailing practices, existing situations, attitudes, reasons, and on-going processes, while the qualitative research approach uses spatial analysis methods (direct assessment of physical characteristics of the selected buildings) and focus group discussion (FGD) sessions with the custodians, prominent elderly persons, or ward head (Mai Unguwa) from each of the selected buildings. In this work, we found it necessary to survey 29 historical buildings of which three of the historic buildings from pre-colonial, colonial, and post-colonial architecture were purposively sampled for inclusion. This is on the basis of their value formation, processes, phenomena, and typology. The findings reveal that deterioration is due to decaying plaster and paint, moist walls, deformed openings, sagging roofs, wall cracks, roof leakages, exit spouts, stains, and corrosion. Other factors include microbes and termite attacks, inappropriate use and neglect, civilization, and inappropriate funding. Conservation was performed to avert the amount of decay while the techniques in practice are documentation methods and treatment interventions with no implementation of diagnostic methods. It further unveils the potential benefits of local treatment, as evidenced by the intervention at the Dorayi palace segment, the use of “makuba” (milled locust bean pod) to stabilize the geotechnical performance of “tubali” (local mud bricks) to improve its potency. This milled locust bean pod also serves as the water repellent consolidant in “laso” (local) plaster, which has proven to be eco-friendly, non-toxic, and effective in wall rendering. The need for immediate implementation of diagnosis techniques in the conservation of architectural heritage in the municipality and elsewhere in Nigeria and beyond is eminent. Intervention and implementation of policies, appropriate funding, and mobilization, raising awareness and sensitization on the value, significance, and state of affairs of our cultural heritage is also paramount. Full article

To further explore the geological structure and the Mesozoic–Paleozoic hydrocarbon prospects in the northern area of the South Yellow Sea (SYS), multiple geological and geophysical data were systematically gathered and compiled, including gravity and magnetic data, seismic surveys, drilling data, and previous research results. The characteristics and genesis of the gravity and magnetic anomalies are examined. This study employs residual gravity anomalies and multiple edge detection methods to identify fault lineament structures and assess the tectonic framework. Moreover, the study utilizes 2.5D gravity-seismic joint modellings and regression analysis to estimate the basement depth. Additionally, the study examines the basement characteristics and discusses the thickness of the Mesozoic–Paleozoic strata. Finally, the study further identifies prospects for hydrocarbons in the Mesozoic–Paleozoic. Our findings show that the faults are incredibly abundant and that the intensity of fault activity weakens gradually from NW to SE. Specifically, NE (NEE) trending faults are interlaced and cut off by NW (NWW), near-EW, and near-SN trending secondary faults, which form an en-echelon composite faults system with a dominant NE (NEE) orientation. Thick Mesozoic–Paleozoic strata are preserved, but we observe distinct variations in basement characteristics and the pre-Cenozoic structural deformation along the N-S direction. Therefore, the Northern Basin of SYS (NBSYS) and the Middle Uplift of SYS (MUSYS) are characterized by alternating sags and bulges in the S-N direction and in the E-W direction, respectively, forming a chessboard tectonic framework. Considering the oil and gas accumulation model, we identify three target hydrocarbon prospects in the NBSYS and two favorable hydrocarbon prospects in the MUSYS. Full article