Transverse Expansion Research Articles

Hadron momentum spectra from analytical solutions of relativistic hydrodynamics

We present analytical solution of relativistic hydrodynamics for a system having cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse expansion. We also consider analytical solution for Hubble-like spherically expanding system. For these two cases, we calculate analytical expression for transverse momentum spectra of hadrons, at constant temperature freeze-out hypersurface using Cooper–Frye prescription. We compare our results for transverse momentum spectra with experimental results from Large Hadron Collider and CERN SPS where one expects cylindrical and spherical geometry of the fireball, respectively. In the case of low-energy collisions with spherical geometry, we calculate rapidity spectra and compare with the results from CERN SPS.

Features of strangeness production in pp and heavy-ion collisions

Based on existing experimental data for A−A collisions starting from the Alternating Gradient Synchrotron energies to those of the CERN Large Hadron Collider, various systematics related to strange hadrons and antihadrons are presented. As in the case of pions, kaons, and protons, the ratio between the average transverse momentum and the square root of the total particle multiplicity per unit rapidity and unit transverse overlap area (〈pT〉/〈dN/dy〉/S⊥) decreases with collision energy and centrality supporting the predictions of the color glass condensate and percolation approaches. The dependencies on 〈dN/dy〉/S⊥ of the slope and offset extracted from the 〈pT〉-particle mass correlation and of the average transverse expansion velocity and kinetic freeze-out temperature, parameters obtained from Boltzmann-Gibbs Blast-Wave fits of pT spectra for strange hadrons, are compared with those for pions, kaons, and protons. The detailed study of the entropy density (〈dN/dy〉/S⊥) dependence of the ratio of strange hadron yields per unit rapidity to the total particle multiplicity per unit rapidity (YS/〈dN/dy〉) at different collision energies and centralities reveals the necessity to study strange hadrons and antihadrons separately. The correlations YS/〈dN/dy〉−〈dN/dy〉/S⊥ for single- and multistrange antihadron yields, as a function of the fireball size, are discussed. The YS/〈dN/dy〉−〈dN/dy〉/S⊥ correlations for combined and separated strange hadron species, at different centralities, clearly show a maximum in the region where a transition from baryon-dominated matter to meson-dominated matter occurs. Comparison with pp experimental data reveals another similarity between pp and Pb-Pb collisions at CERN Large Hadron Collider energies. To facilitate a possible comparison with theoretical approaches, the different correlations are either fitted with suitable functions or the corresponding experimental data are provided. Published by the American Physical Society 2025

Research on Composite 3D Well Pattern for Blocky Heavy Oil in Offshore Areas: Transition from Huff-and-Puff to Displacement-Drainage

In view of the deep burial depth, high formation pressure, and presence of top and bottom water in offshore extra-heavy-oil reservoirs, this paper conducts a study on the production performance and flow field variation law of steam huff-and-puff to steam flooding conversion in thick heavy-oil reservoirs based on physical simulation, and analyzes the development effect of the conversion from steam huff-and-puff to steam flooding. On this basis, by comprehensively considering the advantages of gravity-assisted steam flooding and a three-dimensional HHSD well pattern obtained from physical simulation experiments, this paper proposes a well pattern development mode of steam huff-and-puff to composite displacement and drainage, and analyzes the development effect of this well pattern mode using the reservoir numerical simulation method. The research results show that, compared with the planar well pattern of steam huff-and-puff to steam flooding conversion, the adoption of the three-dimensional well pattern can significantly improve the degree of reservoir production and the expansion dynamics of the steam chamber, and mitigate adverse effects such as the increase in water cut caused by top and bottom water on thermal recovery. The composite development of steam huff-and-puff to composite displacement and drainage can be divided into three stages: thermal communication, gravity drainage-assisted steam flooding, and thermal breakthrough erosion and oil washing. The steam chamber presents a development mode of “single-point development–rapid longitudinal expansion–rapid transverse expansion upon reaching the top–polymerization into a sheet”, and simultaneously possesses the oil displacement mechanisms of both steam displacement and gravity drainage. The proposed composite mode of steam huff-and-puff to composite displacement and drainage has guided the implementation of adjustment wells in the Bohai L Oilfield, and the recovery factor has been increased by about 20% compared with the steam huff-and-puff development of the basic well pattern. This study has reference and guiding significance for the efficient thermal recovery development of this oilfield.

The antagonistic effects of red and blue light radiation on leaf and stem development of pepper (Capsicum annuum L.) seedlings

Light spectrum plays an essential role in influencing the growth and development of vegetable seedlings in industrial seedling raising. Currently, blue light, red light, and their combination are utilized in industrial seedling raising. However, the theoretical basis behind the screening of red and blue light combinations remains unclear. Therefore, we utilized pepper seedlings to investigate the effects mechanism of B (blue light, 450 nm) and R (red light, 660 nm) light-emitting diodes (pc-LED) on stem and leaf development，the full spectrum light was used as a control (W). The growth of pepper seedlings was evaluated by measuring indicators such as leaf, stem growth, and cellular ultrastructure, and try to reveal the regulatory pathways of auxin in leaves at the level of gene expression and transcriptome analysis. The results indicated that compared to W, the blue light led to shorter internodes and reduced plant height, while the red light resulted in larger leaves and elongated internodes of pepper seedlings. Ultrastructural analysis revealed that the antagonism was associated with the longitudinal elongation and transverse expansion of the stem and the expansion efficiency of leaf epidermal cells. Further analysis indicated that cell proliferation and leaf growth were regulated by the phytohormone pathway through light signaling. The blue light upregulated the expression of CaRAX in the phytohormone pathway, while red light increased the expression of CaGRF and CaARF, thereby influencing leaf size. These findings offer new insights into spectral screening for industrial seedling cultivation.

Integrated manufacturing method of multimaterial sand mold by binder jetting

PurposeThis paper aims to develop a flexible manufacturing method for multimaterial sand molds to realize efficient additive manufacturing of multimaterial sand molds.Design/methodology/approachTo study the influence of multimaterial sand laying process parameters on the quality of powder bed and optimize the design of multimaterial sand laying device. Numerical simulation and X-ray Computed Tomography are used to study the penetration behavior and curing morphology of resin in different sand particles.FindingsThe surface roughness and porosity of the multimaterial powder bed that meet the requirements of sand-based additive manufacturing can be obtained under the optimal printing process, that is, the sanding speed of 140.0 mm/s and sanding roller diameter of 15.0 mm. The resin penetration process of the multimaterial sand molds shows a pattern of transverse expansion and longitudinal penetration. In terms of the resin curing morphology, the maximum thickness of the resin film layer of zircon sand reaches 30.5 ± 1.0 µm, which has the best tensile property, followed by silica sand and the thinnest resin film layer of chromite sand.Originality/valueIn this work, a highly flexible integrated combined sand-laying device suitable for multimaterial sand-laying tests is developed, which can obtain a multimaterial powder bed that meets the needs of sand additive manufacturing. Subsequent casting print tests also verify that the program can meet the needs of multimaterial sand mold additive manufacturing.

Comparison of clinical efficiency between pendulum and distal jet appliance - A randomized control trial

The study was to compare the clinical efficiency of Pendulum and distal jet appliances using both cephalometric parameters as well as dental cast analysis at two-time intervals T1-pre-treatment and T2-post-distalization. 10 patients with Angle's Class II malocclusion were enrolled in the study. The patients were divided into two groups: pendulum group & distal jet group (n = 5) for intra oral molar distalization. Lateral cephalogram and dental cast were obtained at T1 and T2. Molar distalization of 4.4 ± 1.1 mm in 4.68 ± 0.67 months in pendulum group and of 3.8 ± 0.4 mm in 5.84 ± 0.7 months in distal jet group. Relative intrusion of upper incisors was found to be more in pendulum group as compared to distal jet group. Mesial tipping of premolars and distal tipping of first molar was observed with both the groups. The transverse expansion at the level of first molars was significantly more in distal jet group as compared to pendulum group. Thus, Pendulum and distal jet appliances were found to be equally effective clinically in distalizing the maxillary molars, although the distalization period was shorter in pendulum group as compared to distal jet group owing to more distal tipping of maxillary first molars in pendulum group. The expansion was significantly more in distal jet group compared to the pendulum group which could be beneficial for patients who have Class II malocclusion with mild posterior crossbite.

Effect of bone-borne maxillary skeletal expanders on cranial and circummaxillary sutures: A cone-beam computed tomography study.

Miniscrew-assisted maxillary expansion devices are frequently used for patients with calcified midpalatal sutures. This study aimed to evaluate the effects of two bone-borne maxillary expansion appliances on the cranial and circummaxillary sutures by comparing cone-beam computed tomography (CBCT) images before and after transverse maxillary expansion. A total of 81 patients (women = 58, men = 23) were treated with either a C-expander (n = 44) or an ATOZ expander (n = 37). CBCT images were obtained before (T0) and after (T1) maxillary expansion, and the widths of 10 circummaxillary sutures were measured in the sagittal, coronal, and axial planes. The Wilcoxon signed-rank test was used to compare the changes in suture width between the C-expander and ATOZ groups, and statistical significance was set at P < 0.05. The frontonasal, frontomaxillary, pterygomaxillary, nasomaxillary, internasal, intermaxillary, and midpalatal suture widths increased significantly after maxillary expansion in both the ATOZ and C-expander groups (both P < 0.05). The frontozygomatic, zygomaticomaxillary, and temporozygomatic suture widths decreased in the C-expander group (P < 0.05), whereas the frontozygomatic suture width increased significantly in the ATOZ group (P < 0.05). The width changes of the frontozygomatic, zygomaticomaxillary, temporozygomatic, pterygomaxillary, internasal, intermaxillary, and midpalatal sutures differed significantly between the two groups (P < 0.05). Both the C- and ATOZ expanders affected the suture width in the naso-maxillo-zygomatic region. The C-expander decreased the circum-zygomatic suture widths, whereas the ATOZ expander widened the frontozygomatic suture with no effect on other circummaxillary sutures.

Effectiveness of dental arch expansion in the orthodontic treatment with clear aligners: a scoping review.

The clinical protocol and effectiveness of dental expansion with Clear Aligner Therapy (CAT), especially among adults is still unclear. There is a need to map and explore knowledge gaps of dental expansion with CAT among children and adults. This scoping review explores the extent and depth of the available literature regarding the effectiveness and predictability of CAT in performing orthodontic expansion in both children and adults. The following databases were consulted as sources of information: PubMed, MEDLINE, Embase, Web of Science, Scopus, LILACS, COCHRANE Library, and ProQuest Dissertations & Thesis, in which the search was limited to studies on children or adults requiring transverse arch expansion and using clear orthodontic aligners. Two independent reviewers assessed the citations and extracted data, which was then synthesized in a narrative format. Over all, 698 citations were retrieved, and 33 were included. Among these, 3 were systematic reviews, 4 were cohort studies, 2 were case-control studies, and 24 were case series. Eighty-five percent of the included studies were published in the last 5 years. Despite different protocols and measurement methods, aligners were effective for arch expansion in adults and children, and the expansion predictability was greater for the lower arch than for the upper arch. The evidence suggests that arch width increment is more predictable in the premolar region and less predictable in the canine and second molar areas, with high variability across studies. Orthodontic aligners have demonstrated effectiveness in expanding arches in both adults and children. However, the literature suggests a decrease in arch width toward the posterior region, and there is no evidence of skeletal gains. To provide more conclusive evidence, randomized controlled clinical studies are warranted. This review was registered in the Open Science Framework database (DOI: https://doi.org/10.17605/OSF.IO/6EG8F).

Effect of time between archwire changes on intended dentoalveolar expansion in orthodontic patients treated with fixed appliances : Aprospective controlled clinical trial.

To analyze the effects of the time span between archwire changes on the amount of transverse dental arch expansion. The design was aprospective, controlled clinical trial. Randomization was performed by computer-generated allocation tables. In all, 35patients were evaluated in three groups treated with fixed appliances and the same four sequential leveling archwires, however, with different replacement periods: 28days (4-week [4W] group), 56days (8-week [8W] group), and 84days (12-week [12W] group). Digital models were measured before the treatment (T0) and at the end of the evaluation period (T1) by ablinded operator with OrthoAnalyzer® software (3-Shape, Copenhagen, Denmark) and compared using MANOVA. Amultiple linear regression was also used to evaluate the influences of age, initial dental crowding, incisor inclination, and facial pattern on the amount of expansion. Mean expansion was 2.77 ± 0.84 mm (upper arch) and 3.12 ± 0.88 mm (lower arch) in the 12Wgroup; 1.96 ± 0.82 mm and 2.27 ± 0.96 mm in the 8Wgroup, and 1.11 ± 0.93 mm and 1.32 ± 0.91 mm in the 4Wgroup, respectively for the upper and lower arches. The amount of expansion varied significantly between the groups in the area of the canines, first premolars, and second premolars for both arches. Expansion was less in older patients. Initial dental crowding, incisor inclination and facial pattern had no influence on dental expansion. Longer time spans between archwire changes provided greater amounts of expansion, while age is inversely related, with younger patients expressing greater amounts of expansion. The results also suggest that the expansion provided by the fixed appliances is expressed mainly in the canine and premolar areas.

Spatiotemporal evolution of post-seismic deformation caused by large earthquakes around the Pacific and its impact on plate movement

SUMMARY The fully relaxed deformation caused by an earthquake refers to the total deformation of the earth caused by the earthquake, including the coseismic deformation and the total effect of post-seismic stress relaxation in the mantle on crustal deformation. An in-depth investigation into post-seismic and fully relaxed deformation resulting from large earthquakes is conducive to comprehending the feedback effect of earthquakes on plate motion. In this paper, we first calculated theoretically the coseimic, post-seicmic and fully relaxed deformations caused by the Tohoku-Oki Mw9.0 earthquake using the spherical dislocation theory. The post-seismic displacement caused by the great earthquake leads to the continuous convergence of plates on both sides of the seismogenic fault, which will certainly facilitate the downward insertion of the subduction plate. As time goes by the influence range of seismic deformations becomes larger and larger. The Tohoku-Oki Mw9.0 earthquake can produce &amp;gt;5 cm of cumulative post-seismic horizontal displacement at a far place like the East Pacific Rise over 100 millenniums. Then, we built slip models of 375 earthquakes with Mw7.0 and above in the circum-Pacific seismic belt, calculated the cumulative post-seismic deformations of them, and found that significant post-seismic horizontal displacements covered the entire Pacific Ocean. The post-seismic deformation field caused by the 2011 Tohoku-Oki Mw9.0 earthquake, the 2010 Chile Mw8.8 earthquake, the 1964 Prince William Sound Mw9.1 earthquake and the 1960 Chile Mw(9.3–9.4) earthquake determines the overall distribution pattern of the deformation field in the Pacific region. Those large earthquakes around the Pacific make the total Pacific Plate present a tension strain in the northwest–southeast direction. The one at the East Pacific Rise reaches 300–400 nstr, with orientation of principle strain approximately perpendicular to the Rise. This tensile strain is bound to encourage transverse expansion of the mid-ocean ridge. By a logical extension, the post-seismic stress relaxation in the mantle caused by past earthquakes should be an important driving force for the current plate movement, in addition to the classic driving force like negative buoyancy and plate material phase transition. This study proves theoretically that there is a two-way relationship between great earthquakes and plate movement, and the viscous structure of mantle plays a key role in the relationship.

Effect of Anchorage Modifications on the Efficacy of Miniscrew-Assisted Rapid Palatal Expansion: A Systematic Review and Meta-Analysis.

Mini-implant-assisted rapid palatal expansion (MARPE) offers a non-surgical alternative for expanding the basal bone, increasing skeletal effects while minimizing undesirable dental side effects. This systematic review and meta-analysis evaluatethe effectiveness of MARPE in terms of transverse skeletal development, dentoalveolar changes, and periodontal effects, with consideration of appliance design. A review was conducted across multiple databases, including PubMed, MEDLINE, Embase, Scopus, and Springer, covering studies published between 2005 and 2024. Randomized controlled trialsinvolving MARPE, with specific attention to design variations (e.g., miniscrew type, number, diameter, length, position, and activation protocol), were selected. Transverse skeletal expansion, assessed via changes in the nasal width, was reported in six of seven studies, with an average increase ranging from 0.31 mm to 2.90 mm for MARPE, compared to 0.11 mm to 2.46 mm for conventional Hyrax expanders. Maxillary width expansion ranged from 2.89 mm to 9.08 mm with MARPE and from 2.59 mm to 8.51 mm with Hyrax. Periodontal changes were reported in six studies, although details were generally unclear. The use of four self-drilling miniscrews with once-daily activation over an extended period produced greater nasal width expansion, greater average skeletal expansion of the maxilla, and less dental inclination and dentoalveolar expansion compared to Hyrax. No significant differences were observed between short and long miniscrews, although wider miniscrews resulted in improved outcomes. The MARPE technique, especially when using a design with four self-drilling miniscrews and daily activation until the targeted expansion is reached, offers notable benefits compared to the conventional Hyrax appliance. This method improves both nasal and maxillary skeletal expansion, lessens dental inclination, and reduces negative effects relative to traditional approaches.

Compressive Mechanical Properties and Energy Absorption of Cubic Spherical Hollow Cellular Material Based on the Rod and Curved Surface Structure

Cellular materials, such as lattices and honeycombs, were widely used for structural protection owing to their excellent mechanical properties. By combining the excellent characteristics of lattice and honeycomb curved surface structures, this study designed a cell called Cubic Spherical Hollow (CSH), which had the advantages of orthogonal isotropy and better spatial connectivity. Inspired by the micro-structural arrangement of bamboo fiber and conch shell, we designed the new CSH cellular materials through the interlayer offset strategy. Then, the effects of interlayer offset on the mechanical properties and compression deformation behavior were explored experimentally and simulatively. Compared with other cellular materials, CSH cellular materials exhibited excellent mechanical properties with higher specific strength and specific modulus. The arrangement offsets of the CSH cells between different layers led to a change in the deformation mechanism from a rod’s compressive mode to a combination of a rod’s compressive mode and curved surface’s bending mode. The initial peak stress and plateau stress decreased with the increased arrangement offsets of the CSH since the extruded protrusions of the structure filled the holes and reduced the lateral expansion behavior of the material in the pressurized environment. This phenomenon also reduced the transverse expansion and prevented the sudden change in stress in the constrained space, indicating that the structural deformation was stable and had excellent cushioning and energy absorption properties. In this study, the cellular material design strategy opens a new avenue for energy absorption.

Probing the shape of the quark-gluon plasma droplet via event-by-event quark-gluon plasma tomography

This study investigates quark-gluon plasma in heavy-ion collisions through two avenues: high-p⊥ frameworks and hydrodynamic modeling. Using the TRENTo model, we find that the p=0 value aligns well with high-p⊥ data, in agreement with Bayesian analysis of the low-p⊥ regime. While adjusting p values may improve a fit to a particular high-p⊥ observable, it does not permit an earlier onset of transverse expansion. Published by the American Physical Society 2024

Research on the Mechanical and Thermal Properties of Carbon-Fiber-Reinforced Rubber Based on a Finite Element Simulation.

The comprehensive performance of rubber products could be significantly improved by the addition of functional fillers. To improve research efficiency and decrease the experimental cost, the mechanical and thermal properties of carbon-fiber-reinforced rubber were investigated using finite element simulations and theoretical modeling. The simplified micromechanical model was constructed through the repeatable unit cell with periodic boundary conditions, and the corresponding theoretical models were built based on the rule of mixture (ROM), which can be treated as the mutual verification. The simulation results suggest that, in addition to the fiber volume fraction Vfc increasing from 10% to 70%, the longitudinal Young's modulus, transversal Young's modulus, in-plane shear modulus, longitudinal thermal expansion coefficient, and transversal thermal expansion coefficient changed from 2.31 × 1010 Pa to 16.09 × 1010 Pa, from 0.54 × 107 Pa to 2.59 × 107 Pa, from 1.66 × 106 Pa to 10.11 × 106 Pa, from -4.98 × 10-7 K-1 to -5.89 × 10-7 K-1, and from 5.72 × 10-4 K-1 to 1.66 × 10-4 K-1, respectively. The mechanism by which Vfc influences the properties of carbon-fiber-reinforced rubber was revealed through the distribution of Von Mises stress. This research will contribute to improving the performance of carbon-fiber-reinforced rubber and promote its application.

Experimental and numerical study of the thermomechanical properties of flexible self-reinforced polyimide composite membrane

Polyimide membranes are favored in the aerospace field for their excellent comprehensive properties, but new application requirements demand higher strength, modulus and thermal expansion properties. Here, self-reinforced polyimide composite membranes (SRPICM) with varying fiber tow arrangement densities were fabricated by unidirectional reinforcement of polyimide fiber tows to enhance the thermomechanical properties of the membranes while maintaining the characteristics of low thickness and flexibility. A micro-scale representative volume element model with interface, and a macro-scale model containing cracks were developed based on the membranes' morphology to investigate the tensile and thermal expansion behavior of SRPICM. Experimental and numerical analyses demonstrated that fiber tows significantly improved the longitudinal tensile properties of SRPICM, with maximum increases in modulus and strength to 34.02 GPa and 1.26 GPa, respectively, over 13 times those of pure PI membranes. Further, the test results, combined with the two-scale finite element model revealed the evolution of longitudinal and transverse tensile deformation and thermal expansion behavior of SRPICM. The validity of the two-scale model was confirmed by experimental results, attributed to the practical consideration of interfacial bonding, prefabricated cracks and thermal residual stress effects during initial modeling. Notably, SRPICM with 10 fiber tows/20 mm arrangement density exhibited excellent longitudinal tensile properties (modulus and strength of 14.01 GPa and 470.89 MPa, respectively) and a longitudinal thermal expansion close to zero (0.03 μm/m°C), making it an ideal material for aerospace applications.

Simulation and Experimental Study on Bridge–Vehicle Impact Coupling Effect under Pavement Local Deterioration

With the rapid development of China’s transportation network, the demand for bridge construction is increasing, the traffic volume is increasing yearly, and the average vehicle speed and the frequency of overloaded vehicles crossing bridges are soaring. When a vehicle passes over a highway bridge, it can easily form a coupling vibration between the vehicle and bridge due to the excitation of the expansion joint, the unevenness of the bridge deck, and the existing coating-hole. The impact effect is significant, which seriously affects the operation safety of both the vehicle and bridge, seriously damaging the service life of the bridge. Due to the influence of construction technology, it is common for the vibration to meet transverse and longitudinal expansion joints of a prefabricated girder bridge, where an aging bridge deck frequently results in bulges and potholes in asphalt pavement. The bridge vibration amplification effect under the dynamic load of heavy, high-speed vehicles is significant, and research about the large impact coefficient of bridges with local pavement deterioration is urgently needed. This study used SIMULINK simulation software and involved conducting several bridge model tests. Dynamic simulation analyses and running vehicle tests on scaled and real bridge models were carried out to study the coupling vibration response of bridge decks in the presence of different pothole sizes. The results show that the impact effect of low-speed vehicles passing through a larger-sized pothole is relatively significant, and the impact coefficient can be amplified to 214% of the original value under good road surfaces in extreme cases. The vehicle–bridge coupling impact effect of potholes is similar to bulges. This relevant work could provide suggestions for the operational performance evaluation and maintenance of bridges with local pavement deterioration.

3D printed auxetic metamaterials with tunable mechanical properties and morphological fitting abilities

Research on creating special structures with a negative Poisson’s ratio, known as auxetic metamaterials, is widely conducted for potential applications in flexible electronics, aerospace, biomedicine, and other fields. Auxiticity is the phenomenon of transverse expansion that occurs when stretched longitudinally. However, conventional metamaterial tunable properties have certain limitations, mainly in the form of limited Poisson’s ratio tuning range and transverse deformation. In this work, a series of symmetric antichiral auxetic structures with significant auxetic effect and low Poisson’s ratio of −5 are designed and fabricated by 3D printing. Based on the manipulating of unit parameters and the use of shape memory polymers, the auxetic metamaterials exhibit tunable mechanical properties and programmable shape memory behaviors. Owing to these features, the auxetic metamaterials are demonstrated to achieve excellent shape-fitting and size-fitting capabilities, which are followed by expanding in a full range to contact any objects (due to auxiticity) and then contract to conform their shapes (due to shape memory). By integrating flexible electromyography(EMG) electrodes, the shape memory auxetic metamaterials can be used as self-adaptive wearable devices to fit with human limbs, which can ensure the good attachment, high signal to Noise Ratio (SNR), and breathability when collect EMG signals.

Ballistic impact wave and back bulge propagation mechanism and blunt trauma assessment of ceramic/UHMWPE composite body armor

With increasing local conflicts worldwide, studying the impact response of body armor is crucial for enhancing soldier survival rates. However, there is still insufficient understanding of the back bulge expansion patterns, the impact waves transmission features, and blunt injury assessing method of body armor. To investigate these problems deeply, the three-dimensional digital image correlation method and numerical models were employed to reveal the ballistic response mechanism of ceramic/ultra-high-molecular-weight polyethylene (UHMWPE) composite body armor impacted by 7.62 mm rifle bullet. This study built theoretical function for the bulge expansion, revealed the wave transmission mechanism and fractures in both materials and their interaction. Firstly, the experiment revealed that the back-face bulge transverse expansion velocity exhibits a double exponential decrease. Secondly, the contour of back-face bulges consistently demonstrated excellent hyperbolic characteristics at various moments. Thirdly, the average Viscous Criterion (VC) and Blunt Criterion (BC) values were 5.37 and 0.95, corresponding to Abbreviated Injury Scale (AIS) values of 6 and 4. Fourthly, the simulation revealed that the ceramics transverse and radial cracks seems primarily induced by shear stress xy; ceramics conical cracks occurring at the boundaries of equivalent stress seems primarily induced by stress in x and y directions. Fifthly, numerical results revealed that the velocity of compression waves within the laminate increases over time in the impact direction and consistent with ceramic velocity impacted on the laminate. These findings lead to experimental and theoretical advances in the impact response mechanism of composite body armor and provide index for improving the protective performance.

Hierarchical Composite with Self-Adaptive Anisotropic Deformation for Thermal Protection System.

Rigid thermal protection materials such as ultra-high-temperature ceramics are desirable for applications in aerospace vehicles, but few materials can currently satisfy the emerging high-temperature sealing requirements for dynamic gaps created by the mismatch of the thermal expansion of different protection layers. Here, we design and fabricate a flexible biomimetic anisotropic deformation composite by multilayer cocuring onto fiber fabrics. It displays superior anisotropic deformation, whose longitudinal expansion ratio is 48 times greater than the transverse expansion ratio at specific temperatures. Furthermore, the ordered carbon structure created by transition-metal-catalyzed graphitization and the C/Si synergistic effect resulting from the combination of biomimetic fiber fabrics and SR enable the in situ formation of a high-temperature-resistant SiC crystalline phase within the char layer, ultimately resulting in exceptional thermal protection properties. By constructing hollow structures in situ, the back temperature of the composite, which is only 4.33 mm thick, is stabilized at 140 °C under the condition of continuous butane flame ablation (1300 °C) for 420 s. Multilayer structure and flexible features can facilitate large-scale preparation and arbitrary cutting and bending, adapted to different thermal protection areas.

Cephalad-caudad vs transverse blunt expansion of low transverse hysterotomy during caesarean section and risk of severe postpartum haemorrhage: A prospective comparative study

BackgroundThe global prevalence of caesarean section as a delivery method is increasing worldwide. However, there is notable divergence among countries in their national guidelines regarding the optimal technique for blunt expansion hysterotomy of the low transverse uterine incision during caesarean section (cephalad-caudad or transverse). AimTo compare the risk of severe postpartum haemorrhage (PPH) between cephalad-caudad and transverse blunt expansion hysterotomy during caesarean section. MethodsThis prospective comparative observational study was conducted in a university maternity hospital. All women who gave birth to one infant by caesarean section after 30 weeks of gestation between November 2020 and November 2021 were included in this study. The exclusion criteria were a coagulation disorder, the presence of placenta previa, multiple pregnancies, or enlargement of the hysterotomy with scissors. The choice between cephalad-caudad or transverse blunt expansion of the low transverse hysterotomy was left to the surgeon’s discretion. The primary outcome measure was severe PPH, defined as estimated blood loss ≥ 1000 ml. Univariate and multivariate analyses were employed to assess the risk of severe PPH associated with the two methods of enlarging the low transverse hysterotomy. ResultsThe study included 850 women, of whom 404 underwent transverse blunt expansion and 446 underwent cephalad-caudad blunt expansion. The overall incidence of severe PPH was 13.3 %. Univariate analysis revealed no significant difference in the frequency of severe PPH between the cephalad-caudad and transverse blunt expansion groups (13.9 % vs 12.6 %; p = 0.61). However, the use of additional surgical sutures (mainly additional haemostatic stitches) was less common with cephalad-caudad blunt expansion (26.7 % vs 36.9 %; p < 0.05). Multivariate analysis showed no significant difference in risk between the two techniques (odds ratio 1.17, 95 % confidence interval 0.77–1.78). ConclusionNo significant difference in the risk of severe PPH was found between cephalad-caudad and transverse blunt expansion of the low transverse hysterotomy during caesarean section.