Search Results (16,195)

This paper focuses on optimisation of material parameters to describe the elastoplastic stress–strain relationship in finite element solvers. Two new methods are introduced to minimise the numerical error that occurs in the interspace between the experimental cyclic stress–strain curve and its representation using multilinear interpolation. Specifically, both methods are integrated into a Prandtl operator approach, which can be used to simulate the elastoplastic response of mechanical components subjected to variable thermomechanical loadings. The improvement as compared to standard interpolation is most substantial when the number of yield planes is limited, especially in the case of bilinear stress–strain curves. The innovation of this study is an algorithm that optimises positions of the stress–strain points across the temperature range of interest considering several input temperatures. It is shown that these methods are especially applicable for optimisation of material parameters when the stress–strain curves are available for a range of test temperatures that are needed for simulating thermomechanical fatigue. The improvement in the interpolation using these methods is exhibited for two materials with available experimental results: stainless steel EN 1.4512 and polyamide PA12. Full article

In the field of acoustic wave detection, optical sensors have significant potential applications in numerous civilian and military fields due to their high sensitivity and immunity to electromagnetic interference. This study designed an undercoupled silica optical waveguide resonator (OWR) with a 2% refractive index contrast. Mode spot converters were introduced at both ends of the straight waveguide to achieve efficient optical transmission between the fiber and the waveguide. The resonator was fabricated using plasma-enhanced chemical vapor deposition (PECVD) and inductively coupled plasma (ICP) etching technologies. The results show that the quality factor (Q-factor) of the resonator reached 2.75 × 10⁶. Compared with a resonator with a refractive index difference of 0.75%, the Q-factor remained at the same order of magnitude while the sensor size was significantly reduced. To achieve high-sensitivity acoustic wave detection, this study employed an intensity demodulation method to realize acoustic wave detection with the resonator. Test results demonstrate that the OWR can detect acoustic signals in the frequency range of 25 Hz to 20 kHz, with a minimum detectable sound pressure of 1.58 μPa/Hz^1/2 @20 kHz and a sensitivity of 1.492 V/Pa @20 kHz. The sensor exhibits a good signal-to-noise ratio and stability. The proposed method shows broad application prospects in the field of acoustic sensing and is expected to enable large-scale applications in scenarios such as communication, biomedical monitoring, and precision industrial sensing. Full article

Graph anomaly detection (GAD) aims to identify nodes or edges that deviate from normal patterns. However, the presence of heterophilic edges in graphs leads to feature over-smoothing issues. To overcome this limitation, this paper proposes the multi-view heterogeneity resistant network (MV-GHRN) model, which progressively purifies heterophilic edges through multi-view collaboration. First, to address the noise sensitivity of single predictions, the method computes post-aggregation (PA) scores for both the original graph and its perturbed versions and performs weighted fusion, leveraging the consistency of multiple prediction perspectives to enhance the reliability of heterophilic edge identification. Second, a cosine similarity view is introduced as a complementary structural perspective, with both views independently completing heterophilic edge pruning to clean the graph structure from both topological and feature dimensions. Finally, a cross-view self-distillation mechanism is designed, using the fused predictions from the two purified views as teacher signals to guide the optimization of each view in reverse, correcting feature biases caused by heterophilic edges. Experiments on benchmark datasets such as YelpChi and Amazon demonstrate that the framework significantly outperforms existing methods. For instance, on the YelpChi dataset, MV-GHRN surpasses the best baseline by 16.8% and 5.2% in F1-Macro and AUC, respectively, validating the effectiveness of the progressive multi-view purification mechanism. Full article

Background/Objectives: Rigid bronchoscopy poses safety challenges due to airway leakage. Although apnoeic oxygenation is a potential strategy, concerns over carbon dioxide (CO₂) retention have limited its adoption. The introduction of high-flow nasal cannula (HFNC) has renewed interest by potentially mitigating CO₂ accumulation during prolonged apnoea. This study investigated changes in the arterial partial pressure of CO₂ (PaCO₂) during apnoeic oxygenation using Optiflow™. Methods: We retrospectively analysed patients undergoing rigid bronchoscopy with HFNC (70 L·min⁻¹) from 2020 to 2022. The apnoeic period was defined from the onset of apnoeic oxygenation to ventilation resumption. Arterial blood gas levels and complications, including arrhythmia and desaturation, were evaluated. Regression analysis was used to evaluate changes over time. Results: Apnoeic oxygenation was performed in 10 male patients (mean age 65 ± 14 years; body mass index 24.75 ± 4.18 kg·m⁻²). The mean duration of apnoea was 33.7 ± 13.7 min, with PaCO₂ rising linearly at 1.50 mmHg/min. No interventions were required to maintain SpO₂ above 91% for all patients. Except for one case of atrial fibrillation that occurred during emergence rather than the apnoeic period, no significant complications were observed. Conclusions: The observed increase in PaCO₂ was lower than in previously reported studies using HFNC via the nares, suggesting that direct delivery of oxygen to the distal airway via bronchoscopy may enhance CO₂ clearance through more effective washout. Apnoeic oxygenation with HFNC could potentially overcome airway leakage for selected patients, but vigilant monitoring remains essential throughout the apnoeic period. Further research is warranted to enhance patient safety. Full article

Additive manufacturing technologies are no longer limited to rapid prototyping but are increasingly used for low-volume production of functional end-use components. Among advanced AM techniques, HP Multi-Jet Fusion (MJF) stands out for its high precision and efficiency. Polyamides, thanks to their balanced mechanical and thermal properties, are commonly used as building materials in this technology. However, these materials are notoriously difficult to bond with conventional adhesives. This study investigates the shear strength of bonded joints made from two frequently used MJF materials—PA12 and glass-bead-filled PA12—using four different industrial adhesives. Experimental procedures were conducted according to ASTM standards. Specimens for single-lap-shear tests were fabricated on an HP MJF 4200 series printer, bonded using a custom jig, and tested on a Zwick-Roell Z250 electro-mechanical testing machine. Surface roughness of the adherends was measured with a 3D optical microscope to assess its influence on bonding performance. The polyurethane-based adhesive (3M Scotch-Weld DP620NS) demonstrated superior performance with maximum shear strengths of 5.0 ± 0.35 MPa for PA12 and 4.4 ± 0.03 MPa for PA12GB, representing 30% and 17% higher strength, respectively, compared to epoxy-based alternatives. The hybrid cyanoacrylate–epoxy adhesive (Loctite HY4090) was the only system showing improved performance with glass-bead-reinforced substrate (16.5% increase from PA12 to PA12GB). Statistical analysis confirmed significant differences between adhesive types (F_3,24 = 31.37, p < 0.001), with adhesive selection accounting for 65.7% of total performance variance. In addition to the experimental work, a finite element-based numerical simulation was performed to analyze the distribution of shear and peel stresses across the adhesive layer using Siemens Simcenter 3D 2406 software with the NX Nastran solver. The numerical results were compared with analytical predictions from the Volkersen and Goland–Reissner models. Full article

Powder coating, as a promising coating material, has attracted widespread attention due to its convenient construction and being a green option, promoting environmental protection. However, the existence of defects such as insufficient leveling and poor mechanical properties of the coating during the coating process limits the further expansion of its application fields. Therefore, for this article, powder coatings with high leveling performance were prepared by composite modification of nylon 12 (PA-12) resin with polyacrylates and ethylene-α-olefin copolymers (POE). The introduction of modified polyacrylates reduces the surface tension of nylon chains, enhancing melt flowability during curing and making the coating surface smooth. Furthermore, by introducing POE, the flexibility of the powder coating was improved, and its fracture elongation increased from 59% for pure PA-12 to a maximum of 234%. This study provides an effective method for the modification of nylon powder coatings and offers new insights into their use in high-performance coating applications. Full article

This study presents a comprehensive investigation into the large-scale production of synthetic and hybrid (nanoparticle-loaded) nanofibers using needleless electrospinning. A diverse range of polymers, including polyamide 6 (PA6) and its other polymer combinations, recycled PA6, polyamide 11 (PA11), polyamide 12 (PA12), polyvinyl butyral (PVB), polycaprolactone (PCL), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyurethane (PU), polyvinyl alcohol (PVA), and cellulose acetate (CA), were utilized to fabricate nanofibers with tailored properties such as polymer solution concentrations and various solvent systems. Furthermore, an extensive variety of nano- and micro-particles, including TiO₂, ZnO, MgO, CuO, Ag, graphene oxide, CeO₂, Er₂O₃, WO₃, MnO₂, and hyperbranched polymers, were incorporated into the polymeric systems to engineer multifunctional nanofibers with enhanced structural characteristics. The study examines the impact of polymer–nano/micro-particle interactions, fiber morphology, and the feasibility of large-scale production via needleless electrospinning. The resulting nanofibers exhibited diameters starting from 80 nm, depending on the polymer and processing conditions. The incorporation of TiO₂, CeO₂, WO₃, Ag, and ZnO nanoparticles into 15% PA6 solutions yielded well-dispersed hybrid nanofibers. By providing insights into polymer selection, nano- and micro-particle integration, and large-scale production techniques, this work establishes a versatile platform for scalable hybrid nanofiber fabrication, paving the way for innovative applications in nanotechnology and materials science. Full article

In single ventricle (SV) patients, veno-venous (VVCs) and major aortopulmonary collaterals (APCs) are common. We aim to determine the differences between patients with and without interventional closure of VVCs or APCs in this single-center, retrospective analysis of 135 SV patients (2006–2021). Anatomical, surgical and clinical features, hemodynamics and PA dimensions were compared. VVC closure was performed in 34 (25%) patients. VVC closure was associated with comprehensive stage I + II (p = 0.05), left PA patch procedure (p = 0.04), Fontan fenestration (p < 0.001), PA pressure >/= 16 mmHg pre-BCPC (p = 0.04) and >/= 15 mmHg pre-TCPC (p = 0.021), lower saturation pre-TCPC (p = 0.04) and smaller PAs (Nakata p = 0.03, total lower lobe index p = 0.001). Patients with VVC closure had a longer hospitalization post-BCPC (p = 0.008) and post-TCPC (p = 0.04) and longer ICU time post-BCPC (p = 0.04). APC closure was performed in 53 (39%) patients. Male sex (p = 0.001), Norwood I procedure (p = 0.04), younger age at BCPC (p = 0.02), higher end-diastolic pressure pre-TCPC (p = 0.04), lower oxygen levels pre-BCPC (p < 0.001) and smaller PAs (Nakata p = 0.08; McGoon p < 0.001) were related to APC closure. Patients with APC closure had a longer hospital (p < 0.001) and ICU (p = 0.005) stay post-TCPC. Significant VVC and APCs are linked to poorer PA growth, worse hemodynamics, lower sats and prolonged hospital/ICU stays, highlighting the need for targeted attention. Full article

Physical activity (PA) is recommended in pregnancy and postpartum to support mental and physical well-being. However, little is known about the association between pregnancy and postpartum PA and interrelated factors in PA engagement. The objectives of this study were to (a) measure and understand PA engagement in pregnancy and postpartum and how related variables (i.e., work status, number of children, time since birth, PA during pregnancy) are associated with postpartum PA and (b) to examine two self-reported methods for assessing PA postpartum: self-reported PA volume and intensity through questionnaire vs. asking whether women met PA guidelines of 150 min of moderate-to-vigorous PA per week. A total of 526 women who had given birth within the past 18 months completed an online questionnaire (majority were Canadian or American). Descriptive statistics were used to assess PA during pregnancy and postpartum, and chi-square analyses were run to assess the association between related variables and to evaluate self-report methods. During pregnancy, 27.4% of women reported meeting PA guidelines and 25.3% reported meeting PA guidelines postpartum. No significant relationship between return-to-work status or number of children and meeting PA guidelines was found. Participants ≤12 weeks postpartum were less likely to meet PA guidelines compared to those >12 weeks postpartum. There was a significant relationship between meeting PA guidelines during pregnancy and engagement in PA postpartum. Lastly, there was a significant relationship between a binary measure of meeting PA guidelines (i.e., yes or no) and calculated PA volume and intensity when provided through type, frequency, and duration. This study provides insights into PA patterns of women during pregnancy and postpartum. Findings highlight the need for targeted interventions to support maternal health and well-being, emphasizing the importance of establishing PA habits during pregnancy to assist in maintenance postpartum. Results also suggest that simplified assessment methods may be effective for monitoring women’s PA, potentially making it easier for healthcare providers to track and promote healthy behaviors among new mothers. Full article

Air-coupled ultrasonic detection demands high transmission performance from piezoelectric micromachined ultrasonic transducers (PMUTs). However, existing microelectromechanical system (MEMS)-based PMUTs deliver limited output, which compromises measurement accuracy and constrains further development. This work proposes a novel PMUT design with a cantilevered, boundary-suspended diaphragm that relieves residual stress, relaxes edge constraints, increases the mechanical degrees of freedom, and enables larger vibration amplitudes. Additionally, this work develops an accurate air-coupling model to predict device performance and a streamlined micro-nanofabrication process for device realization. Experimental results show that under a 1 Vpp (−5 Voffset) drive, the device achieves a peak acoustic pressure of 4.004 Pa at 69.3 kHz, measured at 10 cm distance in air, corresponding to a maximum sound pressure level of 106.02 dB (re 2 × 10⁻⁵ Pa). Compared to a traditional PMUT at 98.45 dB, this represents a 7.57 dB improvement and, to our knowledge, the highest reported sound pressure level at 10 cm for a single PMUT operating near 70 kHz under a 1 Vpp excitation. These results validate the significant enhancement in transmission performance achieved by the proposed topological structure, offering a solution to overcome the common bottleneck of insufficient output in PMUTs, and indicate strong potential for broader air-coupled sensing applications. Full article

Multiplexed detection of arboviruses using a 4 × 4 Si-based electrolyte-gated transistor (EGT) array functionalized with specific aptamers has been investigated. The Si-based EGTs were fabricated using conventional Si microfabrication processes. The EGTs showed excellent intrinsic electrical characteristics, including a low threshold voltage of 0.8 V, a sub-threshold swing of 75 mV/dec, and a gate leakage of <10 pA, ensuring uniform device performance with low device-to-device variation. Aptamers specific to the yellow fever virus nonstructural protein 1 (YF), dengue virus nonstructural protein 1 (DN), and chikungunya virus envelope protein 2 (CHK) were functionalized on EGT arrays to evaluate individual and multiplexed detection. In individual-target detections, concentration-dependent negative shifts in threshold voltage were observed, and relevant limits of detection (LOD) as low as 38.6 pg/mL, 95.2 pg/mL, and 1.6 ng/mL were extracted for YF, DN, and CHK, respectively. In multiplexed detections, sensitivities decreased and variations increased relative to the individual responses, resulting in higher LODs. The extracted LODs were 0.2 ng/mL, 0.6 ng/mL, and 2.8 ng/mL for YF, DN, and CHK, respectively, which are lower than those reported for other methods. These results suggest that Si-based EGT arrays are promising as a scalable, low-cost, and highly sensitive biosensing platform for multiplexed arbovirus detection and point-of-care diagnostics. Full article

Anxiety disorders affect over 280 million people globally and are associated with cognitive impairment. University students show a particularly high susceptibility, with studies reporting prevalent daily anxiety in this population. Physical activity (PA) has demonstrated efficacy in reducing stress and anxiety, potentially enhancing cognitive function. This scoping review examines existing evidence on the relationship between PA, anxiety symptoms, and academic performance in university students while identifying research gaps. Following PRISMA-ScR guidelines and Arksey and O’Malley’s framework, we analyzed observational and experimental studies from PubMed, Cochrane, Web of Science, and Scopus. A descriptive–analytical approach assessed the effects of exercise on anxiety and academic outcomes. Out of 362 records screened, 27 met the inclusion criteria. Evidence suggests PA interventions across intensity levels may alleviate anxiety symptoms and improve academic performance. However, experimental studies specifically targeting this population remain scarce. Current findings indicate PA interventions may reduce anxiety and potentially enhance academic performance in university students. Further experimental research is required to establish causality and elucidate underlying mechanisms. Full article

Background/Objectives: The benefits of physical activity (PA) do not depend on the PA level alone but also on sedentary behavior (SB). The interaction between PA and SB (i.e., PA–SB interplay) is important to determine one’s health status. This study explored the effect of PA–SB interplay on balance and gait in healthy young adults. Methods: Healthy young adults (n = 133, 18–35 yrs) were placed in four PA–SB interplay groups (according to their sitting duration and physical activity duration) using the American College of Sports Medicine PA guidelines (i.e., sedentary active [>6 h/day, >150 min/week], sedentary inactive [>6 h/day, <150 min/week], physically active [<6 h/day, >150 min/week], and physically inactive [<6 h/day, <150 min/week]). In this cross-sectional study, participants’ balance and gait were assessed with inertial measurement units placed on seven bodily sites. In this exploratory study, significance level was set at p < 0.1. Results: Sway acceleration RMS during the eyes closed on stable surface balance test showed a statistically significant difference among the PA–SB interplay groups (p = 0.055) which was found between sedentary active and physically inactive (p = 0.066). Anticipatory postural adjustment (APA) duration during gait showed a statistically significant difference (p = 0.010) which was found between sedentary inactive and physically active (p = 0.019) and between sedentary active and physically active (p = 0.026). Conclusions: PA–SB interplay influences static (sway acceleration RMS) and dynamic (APA duration) balance of healthy young adults. Findings suggest that somatosensory processing during balance and gait initiation are significantly impacted by PA–SB interplay. Full article

Introduction: Numerous overuse injuries affecting the lower limbs of elite athletes have been associated with biomechanical alterations in plantar loading of the foot. This study aimed to analyze the plantar pressure distribution in elite male soccer players and its relationship with various morphological and functional factors, including foot type, metatarsal and digital alignment, and on-field position. Material and Method: Dynamic foot pressure measurements were obtained from 21 soccer players who participated in the UEFA Champion League. The participants had an average age of 27 years, with an average height of 180.9 cm, weight of 76.9 kg, and BMI of 23.4. An insole system (BioFoot/IBV) with telemetry transmission was employed to record plantar loading patterns during normal gait and running. Results: During the support or contact phase, the central and medial metatarsal areas exhibited the highest peak pressure under both walking and running conditions. When walking, the right foot exerted 13–60% more pressure on the outer metatarsal and toe areas. The left foot experienced up to 13% more peak pressure in the middle metatarsal area. During running, the total pressure difference between the feet ranged from −8% to +19%. The right foot usually had more peak pressure on the heel and first toe. In players with valgus feet, the pressure in the central metatarsal area increased from 1086 kPa (walking) to 1490 kPa (running), representing a 37% increase. Conversely, in players with cavus-varus feet, the pressure in this central area increased from 877 kPa to 1804 kPa, a 105% increase. Conclusions: Foot morphology and playing position significantly influenced the plantar pressure patterns in elite soccer players. The central metatarsal region bears the highest load, particularly during running, with distinct variations across foot types and field positions. These findings highlight the need for individualized biomechanical assessments to prevent overuse injuries and optimize performance. Full article

The risk of soil compaction by agricultural machinery threatens the structure and productivity of tilled soils. However, a quantitative understanding of how specific compaction loads alter the three-dimensional (3D) macropore architecture of tilled soil is still limited. This study employed X-ray computed tomography (CT) to quantitatively characterize the evolution of the 3D macropore network in clay soil under a series of controlled compaction pressures (0, 30, 60, 90, and 120 kPa). Our results revealed a non-monotonic response of macropore number to compaction, which initially increased due to the fragmentation of large pores before declining, peaking at 90 kPa. Most critically, we identified 90 kPa as a critical threshold, beyond which macroporosity and the volume of elongated beneficial pores underwent drastic reductions of 64.8% and 46.6%, respectively. Compaction significantly reduced pore connectivity and surface area, with larger macropores (>1000 μm) proving most vulnerable. The study establishes a quantitative link between applied pressure and specific pore-scale damage, providing a scientific basis for designing agricultural machinery with ground pressures below this critical threshold to preserve soil structure and function after tillage. Full article