Search Results (66)

This study investigates the effect of Interlayer Dwell Time (IDT) on the thermal behavior of the Wire-Laser Directed Energy Deposition (WLDED) process. A two-dimensional transient thermal model was developed in MATLAB, incorporating temperature-dependent material properties, a moving Gaussian heat source, and melting–solidification phase change to simulate sequential layer deposition. The model was calibrated for thin-walled geometries, numerically validated using ANSYS, and experimentally validated with literature data. Using the validated model, twenty-seven cases were simulated to examine the combined influence of IDT, part length, and layer thickness on melt-pool dimensions and layer-wise temperature distribution. The results show that increasing IDT reduces melt-pool depth and length by limiting heat accumulation, with the magnitude of this effect depending strongly on part length and layer thickness. Shorter parts and thicker layers exhibit the highest sensitivity to IDT variations. Additionally, the Thermal Stability Factor (TSF) is introduced, a dimensionless index that effectively identifies heat-accumulation phenomena and indicates thermal instabilities. Overall, the findings enhance the understanding of the impact of IDT in the thermal profile of WLDED and demonstrate that optimized IDT selection can stabilize melt-pool geometry and reduce thermal buildup, supporting future adaptive IDT strategies in wire-based metal additive manufacturing. Full article

Background: Obstructive sleep apnea (OSA) is a heterogeneous disorder traditionally classified and stratified by the apnea–hypopnea index (AHI), which fails to capture variability in symptom burden, comorbid associations, and treatment responses. Clinical phenotyping has emerged as a promising strategy to improve disease characterization and management over the last decade. Methods: We conducted a narrative literature review of studies published between January 2014 and December 2022 that used cluster analysis to define OSA phenotypes in adults with moderate-to-severe disease (AHI ≥ 15 events/h). Eligible studies employed validated questionnaires, symptom reporting, and comorbidity profiling to identify subgroups. Findings were summarized across diverse populations, with emphasis on phenotype reproducibility, comorbidity associations, and treatment implications. Results: Across international cohorts, three reproducible symptom-based phenotypes were consistently identified: excessively sleepy (ES), disturbed sleep (DS), and minimally symptomatic (MS). Additional subtypes, such as upper airway dominant (UA) and moderately sleepy (MoS), were described in larger cohorts. Phenotypes differed in demographic profiles, comorbidity burden, and treatment adherence. ES patients exhibited the greatest symptom burden, higher cardiovascular risk, and better adherence to positive airway pressure (PAP) therapy, with significant symptomatic improvement. DS patients frequently reported insomnia symptoms, showed modest PAP-related gains, and may benefit from adjunctive insomnia-targeted interventions. MS patients, despite low symptom burden, often carried substantial comorbidity risk, specifically buildup of OSA-related cardiovascular risk. Conclusions: Symptom-based OSA phenotypes are reproducible across diverse populations and provide clinically meaningful insights beyond AHI. They allow for improved risk stratification, highlight gaps in detection of minimally symptomatic patients, and inform personalized treatment strategies. Integrating phenotyping into clinical practice has the potential to enhance diagnostic accuracy, optimize therapeutic outcomes, and refine cardiovascular risk prediction in OSA. Full article

Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) is becoming more common among adolescents, but non-invasive biomarkers for early detection are still limited. Liver-expressed antimicrobial peptide-2 (LEAP-2), a ghrelin receptor antagonist, has been connected to obesity and liver fat buildup in adults, but pediatric data are limited. This study investigates the hypothesis that higher levels of LEAP-2 are associated with hepatic steatosis and the role of LEAP-2 serum levels in the earlier and easier diagnosis of MASLD in children. Methods: In this cross-sectional study, 51 adolescents aged 12–18 were divided into three groups: one with MASLD and obesity (MASLD-Ob) (confirmed hepatosteatosis by imaging studies such as magnetic resonance or ultrasound, along with at least one cardiometabolic criterion and a body mass index (BMI) > 2 SD) (n = 19), another with obesity without any liver pathology or MASLD (BMI > 2 SD) (n = 14), and healthy controls (n = 18). The controlled attenuation parameter (CAP) was measured using FibroScan^® Mini + 430 (Echosens SA, Créteil, France), and serum ghrelin and LEAP-2 levels were determined via ELISA. Correlations between LEAP-2, ghrelin, CAP, BMI z-score, and metabolic parameters were analyzed. Results: LEAP-2 and ghrelin levels among the three groups were similar (p = 0.148, p = 0.515). A positive correlation was observed between LEAP-2 levels and CAP values in the obese group (both the MASLD-Ob and obesity groups) (r = 0.379, p = 0.030). When a cutoff of 240 dB/m was used, the median LEAP-2 level in cases above this value was 2.20 ng/mL, compared to 1.37 ng/mL in cases below it (p = 0.021), which was significantly different. When analyzing the obese group (both the MASLD-Ob and obese groups) a statistically significant correlation was found between serum LEAP-2 levels and CAP, AST, GGT, and total bilirubin values (r = 0.379, p = 0.030; r = 0.369, p = 0.035; r = 0.369, p = 0.035; r = 0.357, p = 0.049, respectively). Conclusions: Interventional imaging methods and biomarkers for diagnosing and monitoring hepatosteatosis have become well-established in the literature. However, since these tests are not available at all centers and can be costly, there is an increasing search for other easily accessible diagnostic and follow-up parameters. LEAP-2 could be a promising non-invasive biomarker for pediatric MASLD, especially when used alongside CAP measurements. The application of this biomarker in pediatric MASLD provides valuable data to help identify and monitor the condition in adolescents. We believe our study offers strong evidence to support further research and the development of drug treatments for MASLD that aim to reduce plasma LEAP-2. Full article

Reliable DC cable insulation is crucial for photovoltaic (PV) systems and high-voltage DC (HVDC) networks. However, conventional materials such as cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC) face challenges under prolonged DC stress—notably space charge buildup, dielectric losses, and thermal aging. Cross-linked polyolefin (XLPO) has emerged as a halogen-free, thermally stable alternative, but its comparative DC performance remains underreported. Methods: We evaluated the insulations of virgin XLPO, XLPE, and PVC PV cables under ±1 kV DC using time-domain indices (IR, DAR, PI, Loss Index), supported by MATLAB and FTIR. Multi-layer cable geometries were modeled in MATLAB to simulate radial electric field distribution, and Fourier-transform infrared (FTIR) spectroscopy was employed to reveal polymer chemistry and functional groups. Results: XLPO exhibited an IR on the order of 10⁸–10⁹ Ω, and XLPE (IR ~ 10⁸ Ω) and PVC (IR ~ 10⁷ Ω, LI ≥ 1) at 60 s, with favorable polarization indices under both polarities. Notably, they showed high insulation resistance and low-to-moderate loss indices (≈1.3–1.5) under both polarities, indicating controlled relaxation with limited conduction contribution. XLPE showed good initial insulation resistance but revealed polarity-dependent relaxation and higher loss (especially under positive bias) due to trap-forming cross-linking byproducts. PVC had the lowest resistance (GΩ-range) and near-unit DAR/PI, dominated by leakage conduction and dielectric losses. Simulations confirmed a uniform electric field in XLPO insulation with no polarity asymmetry, while FTIR spectra linked XLPO’s low polarity and PVC’s chlorine content to their electrical behavior. Conclusions: XLPO outperforms XLPE and PVC in resisting DC leakage, charge trapping, and thermal stress, underscoring its suitability for long-term PV and HVDC applications. This study provides a comprehensive structure–property understanding to guide the selection of advanced, polarity-resilient cable insulation materials. Full article

Aiming at the lightweight design of a bridge-shed integration structure, this paper presents a three-layered absorbing system in which a part of the sand cushion is replaced by expanded polystyrene (EPS) geofoam and the reinforced concrete (RC) protective slab is arranged above the sand cushion to enhance the composite system’s safety. A three-dimensional Smoothed Particle Hydrodynamics–Finite Element Method (SPH-FEM) coupled numerical model is developed in LS-DYNA (Livermore Software Technology Corporation, Livermore, CA, USA, version R13.1.1), with its validity rigorously verified. The dynamic response of rockfall impacts on the shed slab with composite cushions of various thicknesses is analyzed by varying the thickness of sand and EPS materials. To optimize the cushion design, a specific energy dissipation ratio (SEDR), defined as the energy dissipation rate per unit mass (η/M), is introduced as a key performance metric. Furthermore, the complicated interactional mechanism between the rockfall and the optimum-thickness composite system is rationally interpreted, and the energy dissipation mechanism of the composite cushion is revealed. Using logistic regression, the ultimate stress state of the reactive powder concrete (RPC) slab is methodically analyzed, accounting for the speed and mass of the rockfall. The results are indicative of the fact that the composite cushion not only has less dead weight but also exhibits superior impact resistance compared to the 90 cm sand cushions; the impact resistance performance index SEDR of the three-layered absorbing system reaches 2.5, showing a remarkable 55% enhancement compared to the sand cushion (SEDR = 1.61). Additionally, both the sand cushion and the RC protective slab effectively dissipate most of the impact energy, while the EPS material experiences relatively little internal energy build-up in comparison. This feature overcomes the traditional vulnerability of EPS subjected to impact loads. One of the highlights of the present investigation is the development of an identification model specifically designed to accurately assess the stress state of RPC slabs under various rockfall impact conditions. Full article

This study presents a simulation-based damage modeling and fatigue risk assessment of a reusable ceramic matrix composite thruster designed for short-duration, green bipropellant propulsion systems. The thruster is constructed from a fiber-reinforced ultra-high temperature ceramic matrix composite composed of zirconium diboride, silicon carbide, and carbon fibers. Time-resolved thermal and structural simulations are conducted on a validated thruster geometry to characterize the severity of early-stage thermal shock, stress buildup, and potential degradation pathways. Unlike traditional fatigue studies that rely on empirical fatigue constants or Paris-law-based crack-growth models, this work introduces a simulation-derived stress-margin envelope methodology that incorporates ±20% variability in temperature-dependent material strength, offering a physically grounded yet conservative risk estimate. From this, a normalized risk index is derived to evaluate the likelihood of damage initiation in critical regions over the 0–10 s firing window. The results indicate that the convergent throat region experiences a peak thermal gradient rate of approximately 380 K/s, with the normalized thermal shock index exceeding 43. Stress margins in this region collapse by 2.3 s, while margin loss in the flange curvature appears near 8 s. These findings are mapped into green, yellow, and red risk bands to classify operational safety zones. All the results assume no active cooling, representing conservative operating limits. If regenerative or ablative cooling is implemented, these margins would improve significantly. The framework established here enables a transparent, reproducible methodology for evaluating lifetime safety in ceramic propulsion nozzles and serves as a foundational tool for fatigue-resilient component design in green space engines. Full article

The ecological environment of Inner Mongolia constitutes a critical component of China’s ecological civilization construction. To comprehensively assess and monitor ecological quality dynamics in this region, this study employed MODIS remote sensing data products (2000–2020) and derived four key indicators, —vegetation index (NDVI), wetness index (WET), build-up and soil index (NDBSI), and land surface temperature (LST)—via the Google Earth Engine (GEE) platform. A Remote Sensing-based Ecological Index (RSEI) was constructed using principal component analysis (PCA) to establish an annual long-term time series, thereby eliminating subjective bias from artificial weight assignment. Integrated methodologies—including Theil–Sen Median and Mann–Kendall trend analysis, Hurst exponent, and geographical detector—were applied to investigate the spatiotemporal evolution of ecological quality in Inner Mongolia and its responses to climatic and anthropogenic drivers. This study proposes a novel framework for large-scale ecological quality assessment using remote sensing. Key findings include the following: The mean RSEI value of 0.41 (2000–2020) indicates an overall improving trend in ecological quality. Areas with ecological improvement and degradation accounted for 76.06% and 23.84% of the region, respectively, exhibiting a spatial pattern of “northwestern improvement versus southeastern degradation.” Pronounced regional disparities were observed: optimal ecological conditions prevailed in the Greater Khingan Range (northeast), while the Alxa League (southwest) exhibited the poorest conditions. Northwestern improvement was primarily driven by increased precipitation, rising temperatures, and conservation policies, whereas southeastern degradation correlated with rapid urbanization and intensified socioeconomic activities. Our results demonstrate that MODIS-derived RSEI effectively enables large-scale ecological monitoring, providing a scientific basis for regional green development strategies. Full article

Urban environments are increasingly affected by extreme weather conditions, posing significant risks to vulnerable populations, such as the homeless. This research applies geospatial analysis to identify areas of extreme heat and moisture within the Athens metropolitan area in Greece. The analysis utilizes satellite-derived land surface temperature (LST), vegetation density index (NDVI), build-up density index (NDBI), Topographic Wetness Index (TWI), and other terrain-based factors to develop high-fidelity risk zones. These zones are critical for informing targeted interventions and policy measures aimed at protecting vulnerable groups from heat waves and extreme moisture. This research integrates a geospatial analysis approach for mapping and evaluating heat and moisture vulnerability zones. This approach integrates remote sensing data, GIS-based modeling, and terrain analysis. The findings can provide local authorities and social services with the necessary information to design adaptive strategies for climate change resilience. Full article

This paper investigates the spillover effects and transmission networks of systemic risk within China’s national economic sectors under extreme conditions from both time and frequency domain perspectives, building upon the spillover index methodology and calculating the ∆CoVaR index for Chinese industries. The findings indicate the following: (1) Extreme-risk spillovers synchronize across industries but exhibit pronounced time-varying peaks during the 2008 Global Financial Crisis, the 2015 crash, and the COVID-19 pandemic. (2) Long-term spillovers dominate overall connectedness, highlighting the lasting impact of fundamentals and structural linkages. (3) In terms of risk volatility, Energy, Materials, Consumer Discretionary, and Financials are most sensitive to systemic market shocks. (4) On the risk spillover effect, Consumer Discretionary, Industrials, Healthcare, and Information Technology consistently act as net transmitters of extreme risk, while Energy, Materials, Consumer Staples, Financials, Telecom Services, Utilities, and Real Estate primarily serve as net receivers. Based on these findings, the paper suggests deepening the regulatory mechanisms for systemic risk, strengthening the synergistic effect of systemic risk measurement and early warning indicators, and coordinating risk monitoring, early warning, and risk prevention and mitigation. It further emphasizes the importance of avoiding fragmented regulation by establishing a joint risk prevention mechanism across sectors and departments, strengthening the supervision of inter-industry capital flows. Finally, it highlights the need to closely monitor the formation mechanisms and transmission paths of new financial risks under the influence of the pandemic to prevent the accumulation and eruption of risks in the post-pandemic era. Authorities must conduct annual “Industry Transmission Reviews” to map emerging risk nodes and supply-chain vulnerabilities, refine policy tools, and stabilize market expectations so as to forestall the build-up and sudden release of new systemic shocks. Full article

Background/Objectives: Regiospecificity in triacylglycerols (TAGs) influences absorption/bioavailability of dietary fatty acids. We evaluated whether sn1,3 located DHA (22:6ω3) of a transgenic higher plant (DHA-Canola^®) preferentially facilitates its tissue incorporation as compared to sn2 positioned DHA (DHASCO^® of algal origin). Methods: Sprague Dawley rats were fed diets (12 weeks) containing DHA-Canola or DHA-Control (a blend of DHASCO^® and high oleic sunflower seed oil (HOSO)) at 0.3%, 1%, 3%, and 6% (w/w), or 7% HOSO prior to determination of tissue fatty acids. Results: At 0.3 and 1% w/w supplementation, plasma, liver and cardiac tissue DHA incorporation was higher in the plant-based oil (DHA-Canola vs. DHA-Control; p < 0.05), whilst sn2 enriched algal oil yielded better outcomes at higher doses (at 3% inclusion, plasma values were 7.8 vs. 5.9%, and at 6% supplementation, 10.0 vs. 7.9 in favor of DHA-Control, p < 0.05) At lower intakes, sn1,3 regiospecificity (DHA-Canola) increased the omega-3 index, a clinically relevant biomarker, compared to DHA-Control (p < 0.05). Similarly, a build-up of 20:5ω3 and 22:5ω3 occurred with DHA-Canola. Consequently, total omega3s were higher in this latter group. Conclusions: At lower intakes, sn1,3 regiospecificity of DHA leads to its preferential tissue incorporation compared to sn2 DHA. Full article

The optical and radiation shielding of PVA have been enhanced through embedding with ZnO/CuO/SWCNT (ZCS) nanocomposites. ZCS polymeric nanocomposites (PNCs) were prepared with the solution casting method. Scanning electron, optical microscopy and FT-IR procedures were performed to examine the surfaces’ morphology and structures’ modifications. UV–visible measurements were carried out to investigate the linear/nonlinear optical properties. The optical investigations show significant alterations in the optical parameters of PVA due to ZCS embedding. The UV–visible analysis shows that the optical parameters, including the transmittance, energy bandgap, refractive index, dielectric constants and optical conductivity of PVA, are tuned through ZCS embedding. The direct and indirect bandgap of PVA shrank from 5.42 eV and 4.99 eV (neat PVA) to 3.20 eV and 2.26 eV (10 wt.% ZCS PNCs). The nonlinear optical (NLO) constants (first order susceptibility (χ⁽¹⁾), third susceptibility (χ⁽³⁾) and refractive index (n₂)) of PVA were improved. Phy-X/PSD software was used to investigate the radiation shielding parameters of all samples. The linear attenuation coefficient (LAC), mean free path (MFP), half value layer (HVL), tenth value layer (TVL) and effective atomic number (Z_eff) of PVA were enhanced through ZCS embedding. It is found that the mass attenuation coefficient (MAC) of the neat PVA increased from 1.14 cm²/g to 7.96 cm²/g at 0.015 MeV. The HVL of PVA decreased from 30.2 cm to 20.6 cm, the TVL decreased from 100.3 cm to 68.5 cm and the MFP decreased from 43.6 cm to 29.8 cm upon embedding 10 wt.% of ZCS NCs at 15 MeV. The samples’ exposure buildup factor (EBF) and energy absorption buildup factor (EABF) in the photon energy range from 0.015 MeV to 15 MeV at 0.5 to 40 MFP values. This study proves that ZCS PNCs are advantageous for applications in optical and radiation shielding fields. Full article

Alkali-activated materials (AAMs) offer an eco-friendly alternative to traditional Portland cement, yet their rheological properties, particularly in concrete mixtures, remain largely underexplored. This study conducted rheological tests to investigate the flow properties and thixotropic behavior of alkali-activated slag (AAS) concrete with varying water-to-binder (w/b) ratios and silicate modulus (Ms). The thixotropy of AAS concrete was assessed using the thixotropic index, breakdown area, and variations in apparent viscosity under different shear rates, revealing correlations between thixotropic behaviors and rheological parameters. Mixtures with lower Ms and w/b ratios showed limited slump values and rapid structural build-up due to increased interparticle connections. As Ms increased, enhanced thixotropic behaviors were observed, attributed to the rapid formation of early hydration products. This led to a significant increase in peak torque values and a slight decrease in equilibrium torque values at various rotational speeds. In turn, AAS concrete with higher Ms demonstrated improved fluidity and workability retention after thixotropic build-up was erased. The results of this study provide valuable insights into the flow and thixotropic behaviors of fresh AAS concretes for practical applications. Full article

The principal purpose of this study is to determine the prevalence of peripheral arterial disease (PAD), as well as the principal associated risk factors, in patients registered in the IDON-PAD database. PAD is a condition characterized by the narrowing or blockage of arteries in the body’s extremities due to plaque buildup, leading to reduced blood flow and tissue ischemia. While PAD primarily affects the lower extremities, it can lead to symptoms such as intermittent claudication and, in severe cases, ulcers and amputations. Risk factors for PAD are numerous and cumulative, including smoking, age over 50, type 2 diabetes mellitus, and hypertension. The prevalence of PAD increases with age, with rates ranging from 2.5% in those over 50 to 60% in those over 85, varying by ethnicity and study population. Diabetic patients face a higher risk of PAD-related complications and have lower success rates with revascularization procedures. The diagnosis of PAD traditionally relied on physical examination and symptoms, but the Ankle–Brachial Index is now a standard diagnostic tool due to its non-invasive nature and reliability. In Mexico, the prevalence of PAD is estimated at 10%, with significant risk factors being the duration of diabetes, hypertension, hypertriglyceridemia, and smoking. Notably, 70% of PAD cases are asymptomatic, emphasizing the importance of proactive screening. This study aimed to determine the prevalence of PAD and associated risk factors in diabetic patients aged 40 and above. The prevalence was found to be 11.2%, with high-risk waist circumference, elevated triglycerides, positive Edinburgh questionnaire, and weak pulses as significant predictors. The detection and management of PAD in diabetic patients require a comprehensive approach, including lifestyle modifications and regular screenings. Prevention strategies should focus on controlling risk factors, including obesity, hypertension, and dyslipidemia. In conclusion, PAD is a prevalent yet underdiagnosed condition in diabetic patients, necessitating proactive screening and comprehensive management to mitigate associated risks and improve patient outcomes. The principal limitation of this study is that, as it uses a cross-sectional methodology and is not an experimental study, although we can establish the prevalence of PAD as well as the associated risk factors, we cannot define causality or determine the hazard ratio for each of these factors. Special thanks to Dr. Leobardo Sauque Reyna and all participants for their contribution to this research. Full article

Aluminium matrix composites (AMCs) represent an important group of high-performance materials. Due to their specific strength and a high thermal conductivity, these composites have been considered for the large-scale production of brake discs. However, preconditioning the friction surfaces is necessary to avoid severe wear of both the brake discs and the brake linings. This can be achieved through controlled friction against commercially available brake-lining materials and the formation of transfer or reactive layers (tribosurfaces). Homogeneous tribosurfaces allow for nearly wear-free brake systems under moderate brake conditions. In this work, preconditioning was carried out with a pin-on-disc tester, aiming for the fast creation of homogeneously formed and stable tribosurfaces. The influence of surface microedges perpendicular to the direction of friction on the machined AMC surfaces on the build-up speed and homogeneity of the tribosurfaces was investigated. The microedges were generated using ultrasonic-vibration-superimposed face turning. Thereby, the vibration direction corresponded to the direction of the passive force. For research purposes, the distance of the microedges was changed by varying the cutting speed and feed. The experiments were carried out using AMC disc specimens with a reinforcement content of a 35% volume proportion of silicon carbide particles. Machining was realised with CVD-diamond-tipped indexable inserts. The evaluation of the generated surfaces before and after preconditioning was achieved using 3D laser scanning microscopy and scanning electron microscopy. It was demonstrated that ultrasonic-vibration-superimposed face turning effectively generated microedges on the AMC surfaces. The results show that larger distances between the microedges enhanced the formation of stable tribosurfaces. Thus, the tribosystem’s steady state was reached quickly. Therefore, the benefits of AMC-friction-surface microstructuring on the generation of tribosurfaces under laboratory conditions were proven. These findings contribute to the development of high-performance AMC brake systems. Full article

In response to the escalating demand for mineral resources and the imperative for sustainable management of natural assets, the development of effective methods for monitoring mining excavations is essential. This study presents an innovative decision-making model that employs a suite of spectral indices for the sustainable monitoring of mining activities. The integration of the Combinational Build-up Index (CBI) with additional spectral indices such as BRBA and BAEI, alongside multitemporal analysis, enhances the detection and differentiation of mining areas, ensuring greater stability and reliability of results, particularly when applied to single datasets from the Sentinel-2 satellite. The research indicates that the average accuracy of excavation detection (overall accuracy, OA) for all test fields and data is approximately 72–74%, varying with the method employed. Utilizing a single CBI index often results in a significant overestimation of producer’s accuracy (PA) over user’s accuracy (UA), by about 10–14%. Conversely, the introduction of a set of three complementary indices achieves a balance between PA and UA, with discrepancies of approximately 1–3%, and narrows the range of result variations across different datasets. Furthermore, the study underscores the limitations of employing average threshold values for excavation monitoring and suggests the adoption of dedicated monthly thresholds to diminish accuracy variability. These findings could have considerable implications for the advancement of autonomous and largely automated systems for the surveillance of illegal mining excavations, providing a predictable and reliable methodology for remote sensing applications in environmental monitoring. Full article