Search Results (127)

We report a new concept of a pressure sensor fully made from polydimethylsiloxane with a solid core and porous cladding that operates through (frustrated) total internal reflection. A flexible and sensitive rectangular cross-section waveguide was fabricated via the casting and molding method. The waveguide’s optical losses can be temperature-controlled during the fabrication process by controlling the quantity of microbubbles incorporated (2% approximately for samples made at 70 °C). By controlling the precuring temperature, the microbubbles are incorporated into the waveguides during the simple and cost-effective fabrication process through the casting and molding method. For these samples, we measured good optical loss tradeoff of the order of 1.85 dB/cm, which means that it is possible to fabricate a solid-core/clad waveguide with porous cladding able to guide light properly. We demonstrated the microbubble concentration control in the waveguide, and we measured an average diameter of 239 ± 16 µm. A sensitivity to pressure of 0.1035 dB/kPa optical power loss was measured. The results show that in a biomedical dynamic pressure range (0 to 13.3 kPa), this new device indicates the critical pressure threshold level, which constitutes a crucial asset for potential applications such as pressure injury prevention. Full article

Background: Active play has been proposed to complement school-based physical activity (PA) and promote increased movement-related activities relevant for the development of motor competence. Guided active play (GAP) paired with cooperative games provides sufficient moderate-to-vigorous physical activity (MVPA) to improve motor competence for younger children. Whether guided active play exhibits physical activity outputs that are related to motor competence is uncertain. This study assessed the strength of relationships between play-based physical activity and movement skills by comparing linear regression and chi-square analyses. Methods: Forty-two children (Mage = 8.8 ± 0.8 years) participated in a community center program. PA was measured via accelerometry for GAP, alongside assessments of anthropometrics, fitness (leg power, strength, VO₂max), and FMS (Test of Gross Motor Development-2). Multiple linear regression analysis examined reciprocal relationships. Chi-square and cross-tabulations analyzed categorical variables based on lab percentiles (low < 33%, high > 66%) for PA energy expenditure (PAEE), intensity (MVPA), FMS, and fitness. Results: GAP MVPA and object control skills (OC) showed positive reciprocal pathways (β = 0.308, β = 0.394; p ≤ 0.05). VO₂max predicted MVPA (β = 0.408; p < 0.01), with leg power related to PAEE (β = 0.456; p ≤ 0.01). Chi-square analysis revealed significant associations between high OC skills and high PAEE (X² = 15.12, p ≤ 0.05), and high individual average scores of OC with high MVPA (X² = 11.90, p < 0.05. The high performance of AP and LP was associated with MVPA and PAEE, respectively. Conclusions: Findings support a positive feedback loop between MVPA and OC skills for GAP. GAP is an effective strategy for program interventions for children 8 to 10-year old. Full article

As the utilization of wind energy continues to expand as a prominent renewable energy source, the application of Darrieus Vertical Axis Wind Turbine (VAWT) technology has expanded significantly. Various passive modification methods have been developed to enhance efficiency and optimize the aerodynamic performance of the rotor through blade modifications. This study presents passive modification method utilizing Kline–Fogleman (KF) blades which incorporate step-like horizontal slats along the trailing edge. Through Computational Fluid Dynamics (CFD) simulations, this study evaluates ten distinct KF blade configurations, varying in step length and depth, with steps positioned on the inner side, outer side, and both sides of the airfoil. The results indicate that the KF blade with a shorter step on inner side, 20%$c$ in length and 2%$c$ in depth, enhances the average power coefficient ($C_p$) by 19% compared to the rotor with a clean blade. However, when horizontal slats are incorporated on both sides of the blade, with dimensions of 50%$c$ in length and 5%$c$ in depth, $C_p$ decreases by 33% compared to the clean blade. This reduction occurs across both low and high tip speed ratio (TSR) ranges. It has been observed that the presence of a high-pressure zone of 200 Pa at the trailing edge disrupts the aerodynamic performance when the KF blade is in the upwind region between the azimuth angles of 45° and 135°. Full article

To address the challenges of high flow resistance and poor temperature uniformity in conventional PCM–liquid cooling hybrid heat exchangers—which significantly impair the performance and lifespan of electronic devices—a topology optimization approach was adopted. A dual-objective function, aimed at minimizing the average temperature and pressure drop, was introduced to reconstruct the cooling channel layout and PCM filling region. A two-dimensional transient thermo-fluid model coupling the solid–liquid phase-change process with coolant flow and heat transfer was established, alongside the development of an experimental platform. A comprehensive comparison was performed against a conventional liquid cooling plate with straight channels. The results showed that the topology-optimized cooling plate exhibited a pressure drop of 15.80 Pa and a pumping power of 1.19 × 10⁻⁴ W, representing reductions of 38.28% and 38.02%, respectively. The PCM solidification time was shortened by 6 min. Under these conditions, the convective heat transfer coefficient (h_w) and performance evaluation criterion (j/f) of the optimized plate reached 1319.06 W/(m²·K) and 0.56, which corresponded to increases of 60.71% and 47.5%, respectively. The topology-optimized configuration significantly improved temperature uniformity and overall cooling performance. As the inlet velocity increased from 0.05 m/s to 0.2 m/s, h_w increased by 38.65%; however, j/f decreased by 57.14%, due to the limited thermal conductivity of the PCMs, resulting in only a slight reduction in the average PCM temperature. Furthermore, the topology-optimized cooling plate demonstrated stronger steady-state regulation capability under fluctuating thermal loads. This study provides valuable insights and design guidance for the development of high-efficiency hybrid liquid cooling plates. Full article

The degree of hydrolytic modification (marked by parameters: extractive capacity, diastatic power and degree of fermentation) in wheat malts significantly influences their quality, determining their potential for use in brewing. Nitrogen fertilisation at a dose of 60 kg N·ha⁻¹ applied in 3-year field experiments had a positive effect on the extractability value of wheat malts, with an average value of 84.51% d.m. The value of diastatic power in the obtained malts, depending on the variety, was on average at the level of 334–414 units W-K (Windisch–Kolbach) and 357–380 units W-K, depending on nitrogen fertilisation. Wort attenuation obtained from the analysed wheat malts was at a similar level (on average 78.1%), except for malt obtained from grain of wheat fertilised with a nitrogen dose of 40 kg N·ha⁻¹, for which significantly lower values were obtained (respectively, by 5.12%). The viscosity parameter of wheat malts, determining the degree of cytolytic modification, varied and averaged 1.95 mPa·s for the variety and for the nitrogen fertilisation applied. In 2-year canopy experiments, at a nitrogen fertilisation level of 60 kg N·ha⁻¹, the Elixer cultivar was characterised by the best indicators of the degree of hydrolytic and cytolytic modification. Full article

The study investigated the effect of osmotic treatment, edible coatings, and reduced pressure on the quality of carrots dried by the microwave–vacuum method (MVD) at 3.5 or 6.5 kPa and microwave power of 250 W. Initial osmotic enrichment (OE) of carrots was carried out in chokeberry NFC juice, and osmotic dehydration (OD) in chokeberry juice concentrate. Coatings were prepared using sodium alginate or citrus pectin solutions of 1.0 or 1.5%. Osmotic treatment, and then drying pressure, had the greatest effect on increasing the dry matter (DM), total phenolic content (TPC), and color changes, but also on decreasing the water activity (AW) of dried carrot. The highest DM (average 98.7%) and the lowest AW (average 0.25) were obtained in OE carrots and dried at 3.5 kPa. Drying carrots, combined with osmotic treatment and coating, increased TPC by 13-fold, from 225 in fresh to 3229 mg GAE/100 g d.m. in dried carrots. Osmotic treatment did not affect the antioxidant activity of DPPH•, but OD significantly increased ABTS•+ compared to the raw material. Coatings had a smaller effect on color changes and antioxidant activity (DPPH• and ABTS•+) and no significant impact on DM and AW. The color changes of the control and coated samples were an increase in color lightness, redness, yellowness, and saturation (vividness), and those subjected to osmotic treatment showed a decrease in these parameters. The lower AW of dried carrots positively affected higher hardness. All samples were sensory accepted, including color, texture, and smell, especially after OD in chokeberry juice concentrate, while crunchiness was the lowest (five out of nine points). Full article

Non-orthogonal multiple access (NOMA) has emerged as a key enabler of massive connectivity in next-generation wireless networks. However, conventional NOMA studies predominantly focus on two-user scenarios, limiting their scalability in practical multi-user environments. A critical challenge in these systems is error propagation in successive interference cancellation (SIC), which is further exacerbated by hardware distortions (HWDs). Hybrid NOMA (HNOMA) mitigates SIC errors and reduces system complexity, yet cell-edge users (CEUs) continue to experience degraded sum spectral efficiency (SSE) and throughput. Cooperative NOMA (C-NOMA) enhances CEU performance through retransmissions but incurs higher energy consumption. To address these limitations, this study integrates intelligent omni-surfaces (IOSs) into a cooperative hybrid NOMA (C-HNOMA) framework to enhance retransmission efficiency and extend network coverage. The closed-form expressions for average outage probability and throughput are derived, and a power allocation (PA) optimization framework is proposed to maximize SSE, with validation through Monte Carlo simulations. The introduction of a novel strong–weak strong–weak (SW-SW) user pairing strategy capitalizes on channel diversity, achieving an SSE improvement of ∼0.48% to ∼3.81% over conventional pairing schemes. Moreover, the proposed system demonstrates significant performance gains as the number of IOS elements increases, even under imperfect SIC (iSIC) and HWD conditions. By optimizing PA values, SSE is further enhanced by at least 2.24%, even with an SIC error of 0.01 and an HWD level of 8%. These results underscore the potential of an IOS-assisted C-HNOMA system with SW-SW pairing as a viable solution for improving multi-user connectivity, SSE, and system robustness in future wireless communication networks. Full article

Recent advances in wireless communications have favored increasing data rates. For this purpose, complex modulation techniques with high peak-to-average power ratios (PARs) have been introduced. Conventional RF power amplifiers (PAs) provide high efficiency only at saturated power levels. At lower power levels, the efficiency decreases significantly. In modulation techniques with high PAR, it is necessary to increase the efficiency at the back-off power levels. Various techniques have been developed for this purpose. Among these techniques, the load-modulated balanced amplifier (LMBA) has come to the fore in recent years. In this article, a power amplifier with 47 dBm (50 W) output power in the frequency range of 1.7 GHz–1.9 GHz, 60.1–63.3% drain efficiency at maximum output power, and 40.5–46.8% drain efficiency at 6 dB output back-off is designed and manufactured by using the LMBA technique. It is also shown that the efficiency of the system increases both at maximum output power and at 6 dB output back-off when using the LMBA technique. In addition, using the PA designed with the LMBA technique having 50 W minimum power, providing drain efficiency of 60% over the entire operating band at maximum power and drain efficiency of 40% or more at 6 dB output back-off, it is seen that better results are obtained compared to similar studies in the literature. Full article

With the continuous increase in the thermal power of electronic devices, air cooling is becoming increasingly challenging in terms of meeting heat dissipation requirements. Liquid cooling media have a higher specific heat capacity and better heat dissipation effect, making it a more efficient cooling method. In order to improve the heat dissipation effect of liquid cooling, a TPMS structure with a larger specific surface area, which implicit function parameters can control, can be arranged in a shape manner and it is easy to expand the structural design. It has excellent potential for application in the field of heat dissipation. At present, research is still in its initial stage and lacks comparative studies on liquid cooled convective heat transfer of TPMS structures G (Gyroid), D (Diamond), and P (Primitive). This paper investigates the heat transfer performance and pressure drop characteristics of a sheet-like microstructure composed of classic TPMS structures, G (Gyroid), D (Diamond), and P (Primitive), with a single crystal cell length of 2π (mm), a cell number of 1 × 1 × 5, and a microstructure size of 2π (mm) × 2π (mm) × 22π (mm) using a constant temperature surface model. By analyzing the outlet temperature $t_{out}$, structural pressure $p$, average convective heat transfer coefficient $h_0$, Nusselt number $Nu$, and average wall friction factor $f$ of the microstructure within the speed range of 0.01–0.11 m/s and constant temperature surface temperature is 100 °C, the heat transfer capacity D > G > P and pressure drop D > G > P were obtained (the difference in pressure drop between G and P is very small, less than 20 Pa, which can be considered consistent). When flow velocity is 0.01 m/s, the maximum temperature difference at the outlet of the four structures reached 17.14 °C, and the maximum difference in wall friction factor $f$ reached 103.264, with a relative change of 646%. When flow velocity is 0.11 m/s, the maximum pressure difference among the four structures reached 8461.84 Pa, and the maximum difference in $h_0$ reached 7513 W/(m²·K), with a relative change of 63.36%; the maximum difference between Nu reached 76.32, with a relative change of 62.09%. This paper explains the reasons for the above conclusions by analyzing the proportion of solid area on the constant temperature surface of the structure, the porosity of the structure, and the characteristics of streamlines in the microstructure. Full article

Many Caribbean low-latitude small island states lack wind maps tailored to capture their wind features at high resolutions. However, high-resolution mesoscale modeling is computationally expensive. This study proposes a statistical–dynamical downscaling (SDD) method that integrates an atmospheric-circulation-type (CT) approach with a high-resolution numerical weather prediction (NWP) model to map the wind resources of a case study, Trinidad and Tobago. The SDD method uses a novel wind class generation technique derived directly from reanalysis wind field patterns. For the Caribbean, 82 wind classes were defined from an atmospheric circulation catalog of seven types derived from 850 hPa daily wind fields from the NCEP-DOE reanalysis over 32 years. Each wind class was downscaled using the Weather Research and Forecasting (WRF) model and weighted by frequency to produce 1 km × 1 km climatological wind maps. The 10 m wind maps, validated using measured wind data at Piarco and Crown Point, exhibit a small positive average bias (+0.5 m/s in wind speed and +11 W m⁻² in wind power density (WPD)) and capture the shape of the wind speed distributions and a significant proportion of the interannual variability. The 80 m wind map indicates from good to moderate wind resources, suitable for determining priority areas for a detailed wind measurement program in Trinidad and Tobago. The proposed SDD methodology is applicable to other regions worldwide beyond low-latitude tropical islands. Full article

Traditional street quality evaluations are often subjective and limited in scale, failing to capture the nuanced and dynamic aspects of urban environments. This paper presents a novel and data-driven approach for objective and comprehensive street quality evaluation using street view images and semantic segmentation. The proposed SP-UNet (Spatial Pyramid UNet) is a multi-scale segmentation model that leverages the power of VGG16, SimSPPF (Simultaneous Spatial and Channel Pyramid Pooling), and MLCA (Multi-Level Context Attention) attention mechanisms. This integration effectively enhances feature extraction, context aggregation, and detail preservation. The model’s average intersection over union, Mean Pixel Accuracy, and overall accuracy achieving improvements of 5.83%, 6.52%, and 2.37% in mIoU, Mean Pixel Accuracy (mPA), and overall accuracy, respectively. Further analysis using the CRITIC method highlights the model’s strengths in various street quality dimensions across different urban areas. The SP-UNet model not only improves the accuracy of street quality evaluation but also offers valuable insights for urban managers to enhance the livability and functionality of urban environments. Full article

The paper presents an innovative method for tackling multi-attribute decision-making (MADM) problems within a hesitant fuzzy (HF) framework. Initially, the paper generalizes the Chi-square distance measure to the hesitant fuzzy context, defining the HF generalized Chi-square distance. Following this, the paper introduces the power average (P-A) operator and the power geometric (P-G) operator to refine the weights derived from Shannon entropy, taking into account the inter-attribute support. Leveraging the strengths of Aczel–Alsina operations and the power operation, the paper proposes the hesitant fuzzy Aczel–Alsina power weighted average (HFAAPWA) operator and the hesitant fuzzy Aczel–Alsina power weighted geometric (HFAAPWG) operator. Consequently, a hesitant fuzzy Aczel–Alsina power model is constructed. The applicability of this model is demonstrated through a case study examining the urban impacts of cyclonic storm Amphan, and the model’s superiority is highlighted through comparative analysis. Full article

In recent years, the optimization of diesel engine exhaust mufflers has predominantly targeted acoustic performance, while the impact on engine power performance has often been overlooked. Therefore, this paper proposes a parallel perforated tube expansion muffler and conducts a numerical analysis of its acoustic and aerodynamic performance using the finite element method. Then, a Kriging model is established based on the Design of Experiments to reveal the impact of different parameter couplings on muffler performance. With transmission loss (TL) and pressure loss (PL) as the optimization objectives, a multi-objective optimization study is carried out using the competitive multi-objective particle swarm optimization (CMOPSO). The optimization results indicate that this method can simplify the optimization model and improve optimization efficiency. After CMOPSO calculation, the average TL of the muffler increased from 27.3 dB to 31.6 dB, and the PL decreased from 1087 Pa to 953 Pa, which reduced the exhaust noise and improved the fuel economy of the engine, thus enhancing the overall performance of the muffler. This work provides a reference and guidance for the optimal design of mufflers for small agricultural diesel engines. Full article

Valorization of agricultural and food by-products (agri-food waste) and maximum utilization of this raw material constitute a highly relevant topic worldwide. Agri-food waste contains different types of phytochemical compounds such as polyphenols, that display a set of biological properties, including anti-inflammatory, chemo-preventive, and immune-stimulating effects. In this work, the microencapsulation of strawberry (Fragaria vesca) plant extract was made by spray-drying using individual biopolymers, as well as binary and ternary blends of pectin, alginate, and carrageenan. The microparticle morphologies depended on the formulation used, and they had an average size between 0.01 μm and 16.3 μm considering a volume size distribution. The encapsulation efficiency ranged between 81 and 100%. The kinetic models of Korsmeyer–Peppas (R²: 0.35–0.94) and Baker–Lonsdale (R²: 0.73–1.0) were fitted to the experimental release profiles. In general, the releases followed a “Fickian Diffusion” mechanism, with total release times varying between 100 and 350 (ternary blends) seconds. The microparticles containing only quercetin (one of the main polyphenols in the plant) showed higher antioxidant power compared to the extract and empty particles. Finally, the addition of the different types of microparticles to the gelatine (2.7 mPa.s) and to the aloe vera gel (640 mPa.s) provoked small changes in the viscosity of the final gelatine (2.3 and 3.3 mPa.s) and of the aloe vera gel (621–653 mPa.s). At a visual level, it is possible to conclude that in the gelatine matrix, there was a slight variation in color, while in the aloe vera gel, no changes were registered. In conclusion, these microparticles present promising characteristics for food, nutraceutical, and cosmetic applications. Full article

In the realm of management decision-making, the selection of green suppliers has long been a complex issue. Companies must take a holistic approach, evaluating potential suppliers based on their capabilities, economic viability, and environmental impact. The decision-making process, fraught with intricacies and uncertainties, urgently demands the development of a scientifically sound and efficient method for guidance. Since the concept of Fermatean fuzzy sets (FFSs) was proposed, it has been proved to be an effective tool for solving multi-attribute decision-making (MADM) problems in complicated realistic situations. And the Power Bonferroni mean (PBM) operator, combining the strengths of the power average (PA) and Bonferroni mean (BM), excels in considering attribute interactions for a thorough evaluation. To ensure a comprehensive and sufficient evaluation framework for supplier selection, this paper introduces innovative aggregation operators that extend the PBM and integrate probabilistic information into Fermatean hesitant fuzzy sets (FHFSs) and Fermatean probabilistic hesitant fuzzy sets (FPHFSs). It successively proposes the Fermatean hesitant fuzzy power Bonferroni mean (FHFPBM), Fermatean hesitant fuzzy weighted power Bonferroni mean (FHFWPBM), and Fermatean hesitant fuzzy probabilistic weighted power Bonferroni mean (FHFPWPBM) operators, examining their key properties like idempotency, boundedness, and permutation invariance. By further integrating PBM with probabilistic information into FPHFSs, three new Fermatean probabilistic hesitant fuzzy power Bonferroni aggregation operators are developed: the Fermatean probabilistic hesitant fuzzy power Bonferroni mean (FPHFPBM), Fermatean probabilistic hesitant fuzzy weighted power Bonferroni mean (FPHFWPBM), and Fermatean probabilistic hesitant fuzzy probabilistic weighted power Bonferroni mean (FPHFPWPBM). Subsequently, a MADM method based on these operators is constructed. Finally, a numerical example concerning the selection of green suppliers is presented to demonstrate the applicability and effectiveness of this method using the FPHFPWPBM operator. Full article