Search Results (3,008)

Reliable electricity supply in Colombia’s Non-Interconnected Zones requires sustainable and low-cost energy technologies. Vertical-axis hydrokinetic turbines are promising for this purpose; however, their relatively low power coefficient remains a major challenge. This study combines transient 2D and 3D $k$–$\omega$ SST computational fluid dynamics (CFD) simulations with hydraulic channel experiments to investigate a hybrid Darrieus–Savonius turbine. A 27-case Design of Experiments (DoE) based on 2D CFD was first applied to screen the effects of rotor radius ratio (RR), attachment angle (AA), and water velocity. Within the investigated design space, the configuration with $\mathrm{R}\mathrm{R}=0.5$ and $\mathrm{A}\mathrm{A}=0^{\circ }$ produced the most favorable average performance. The selected configuration was subsequently analyzed using 3D CFD and experimentally evaluated at TSR values of 1.0, 1.1, and 1.2. At TSR = 1.0, the 3D model predicted ${\mathrm{C}}_{\mathrm{P}}=0.1525$, closely matching the experimental value of 0.1541 with a relative error of 1.05%. The results demonstrate that 2D CFD is useful for computationally efficient parameter screening and qualitative trend identification, but it overpredicts absolute performance because it neglects blade tip vortices, spanwise flow, and volumetric wake interactions. Three-dimensional CFD is therefore required for reliable performance prediction and analysis of the complex flow structures governing hybrid hydrokinetic turbine behavior. Full article

Public owners selecting design-build (DB) teams for sustainable buildings must justify how proposal evidence, long-term asset performance, and procurement accountability support a preferred contractor. Prior contractor-selection and hybrid MCDM studies provide criteria and ranking tools, but they rarely connect public-building requirements, mandatory floors, proposal evidence anchors, weighting, scoring, and auditability before mathematical ranking. The aim of this study is to develop and numerically demonstrate an evidence-traceable SWOT-AHP-TOPSIS framework for sustainable DB contractor selection in California courthouse procurement. Here, California courthouse procurement refers to public-owner procurement of judicial courthouse facilities in California, United States, under public-building procurement rules and publicly available RFQ/RFP-related records. The framework fixes source-linked criteria, SWOT role definitions, benefit directions, evidence anchors, and compliance floors before criteria weights are obtained using AHP and alternatives are ranked using the TOPSIS method. The proof of concept derives 16 criteria from procurement guidance, California courthouse records, and the literature; reports local and global criteria weights obtained using AHP; and compares synthetic proposal archetypes. Under baseline illustrative weights, A1 ranks first (C* = 0.6548), followed by A3 (0.5804) and A2 (0.3294). Robustness checks using the disclosed matrices show conditional stability: vector, min–max, and linear-sum TOPSIS, equal-criterion weights, weighted-sum comparison, grouped +20% scenarios, comparison-set checks, and 10,000-run Monte Carlo perturbation retain A1 most frequently. The Monte Carlo run selected A1 first in 79.80% of simulations, A3 in 20.19%, and A2 in 0.01%, with top-two practical ties in 7.10% of runs. The results demonstrate arithmetic consistency, reproducibility, and interpretable ranking behavior under stated synthetic assumptions; they do not establish actual evaluator preferences, real proposal quality, award outcomes, or generalizability beyond California courthouse settings. Full article

A lightweight and high-strength structural system is increasingly demanded in prefabricated and sustainable construction; however, accurately evaluating the mechanical behavior of novel composite members remains challenging. This study proposes an aluminum alloy foam concrete composite column consisting of an embedded aluminum alloy frame and foam concrete infill. Material tests, a full-scale axial compression test, and finite element-based parametric analyses were conducted to verify the hypothesis that composite action between the embedded aluminum alloy frame and foam concrete governs the axial load-transfer mechanism and bearing capacity of the proposed column. The results show that initial cracking mainly occurred in the middle region of the column along the diagonal brace direction, while the composite column maintained favorable elastic performance under relatively high load levels. The aluminum alloy frame provided a semi-passive confinement effect on the foam concrete, although this effect gradually weakened with increasing load due to lateral deformation of the diagonal braces. Moreover, an appropriate arrangement of interlocking keys significantly improved the composite action and overall stability of the column. These findings provide experimental and numerical evidence for assessing the axial compression performance of aluminum alloy foam concrete composite columns and offer guidance for the design and optimization of this novel lightweight structural system. Full article

The development of sustainable materials for additive manufacturing (AM) has positioned starch as a compelling alternative to conventional thermoplastics. However, the successful implementation of starch in 3D printing (3DP) relies on precise control of its supramolecular organization, rheological behavior, and processing conditions. This article analyzes starch-based hydrogels for extrusion-driven AM, establishing explicit links between molecular architecture, gelatinization, and viscoelastic performance. The influence of key rheological parameters on extrudability and shape fidelity is examined in parallel with critical processing conditions. Chemical and physical modification routes of starch are compared in terms of their structural impact and printability enhancement. The integration of additives such as polysaccharides, proteins, and inorganic salts is discussed as a strategy to overcome intrinsic mechanical limitation. Emerging non-food application in drug delivery, tissue engineering, or conductive/intelligent hydrogels demonstrates the expanding technological relevance of starch-based formulation. Remaining challenges include predictive, rheology-based design, and the development of multifunctional 4D-printing capabilities. Progress in this field is crucial for positioning starch as a robust platform for sustainable AM, but, despite this progress, a systematic and quantitative framework linking starch molecular architecture and rheological behavior to printing-process parameters and outcomes is still lacking, thus constituting the central gap addressed in this review. Full article

Accelerating aridity and desertification driven by global climate change pose growing threats to dryland forest plantations, making it essential to understand transpiration dynamics across developmental stages for both forest-hydrology theory and the sustainable management of protective shelterbelts. This study compared transpiration characteristics, stomatal conductance (g_s), and water-regulation strategies between a 41-year-old mature stand and a 13-year-old young stand of Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) on the southern margin of Horqin Sandy Land during the 2024 growing season, using thermal-dissipation sap-flow measurements combined with meteorological monitoring and water-potential sampling. Mean individual-tree daily transpiration in the mature stand (2.36 mm·d⁻¹) was approximately 2.6 times that of the young stand (0.90 mm·d⁻¹), yet the young stand showed a disproportionately stronger sap-flow response to small rainfall events. Sap flow in both stands was jointly driven by vapor pressure deficit (VPD) and photosynthetically active radiation, with a near-synchronous lag of ±10 min and tight canopy-atmosphere coupling (decoupling coefficients: 0.177 and 0.256, respectively), indicating transpiration was predominantly governed by stomatal regulation. Stomatal conductance declined with rising VPD in both stands, with a steeper decline in the mature stand. Water-potential analysis revealed pronounced anisohydric behavior in the mature stand (σ = 2.643, R² = 0.765, p < 0.01), and near-strict anisohydric regulation in the young stand (σ = 0.919, R² = 0.105, p > 0.05), indicating high tree-level hydraulic variability and precluding a definitive classification along the iso/anisohydric continuum for this developmental stage. Both g_s and transpiration increased with tree size, contradicting the hydraulic limitation hypothesis. These findings elucidate distinct water-use strategies between the young and mature Mongolian pine stands in this paired design and provide a physiological basis for stage-differentiated, precision water management of dryland shelterbelt plantations. Full article

The increasing generation of construction and demolition waste, along with the depletion of natural aggregates, has driven growing interest in recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) as sustainable alternatives in concrete production. However, a direct and systematic comparison between the two materials remains limited. This review addresses this gap by applying PRISMA guidelines to analyze 82 peer-reviewed studies published between 2010 and 2026. Both materials are evaluated across three key domains: physical properties, mechanical performance, and microstructural characteristics. The findings indicate that RCA can reduce compressive strength by up to 26%, mainly due to the presence of porous adhered mortar and a complex interfacial transition zone (ITZ). In contrast, RAP weakens bonding with cement paste because of its hydrophobic bituminous coating, leading to adhesive failure at the mortar asphalt interface. Despite these limitations, RCA and RAP exhibit distinct behaviors in terms of shear capacity, ductility, energy absorption, and durability. Enhancement techniques such as surface treatment, carbonation, supplementary cementitious materials, and fiber reinforcement show potential in improving performance. Additionally, life cycle and economic analyses reveal that RAP can reduce total costs and carbon emissions when efficiently processed. This study provides a unified comparative framework to support sustainable material selection and design optimization. Full article

The transition from conventional silica nanoparticle (SiNP) production based on purified alkoxysilanes and high-temperature flame hydrolysis of silicon tetrachloride to renewable and waste-derived silicon resources requires more than precursor substitution. It requires a mechanistic understanding of how feedstock mineralogy, silicon speciation, impurity chemistry, and processing history propagate through dissolution, nucleation, condensation, gelation, aging, drying, and pore evolution to determine material performance, environmental burden, and manufacturing feasibility. Although previous reviews have established the technical feasibility of producing silica from secondary resources, their predominant organization by feedstock, synthesis route, or application provides limited ability to explain why nominally similar processes generate materials with markedly different structural and functional properties. This review addresses these through a resource-pull, feedstock-to-function framework that links resource chemistry and process design to critical material attributes, application-specific specifications, sustainability, and scale-up requirements. Agricultural residues, industrial by-products, geothermal resources, waste glass, and fluorosilicate streams are critically compared according to silicon form and phase, reactivity, impurity profile, compositional variability, purification demand, and attainable product quality. Particular attention is given to waste-derived alkaline silicate systems, in which molecular, oligomeric, and colloidal silica coexist and therefore require characterization beyond bulk SiO₂ concentration. Established and emerging processing strategies, including controlled combustion and alkaline extraction, alkali fusion, ambient-pressure drying, microwave and mechanochemical activation, biogenic and biomimetic templating, and continuous processing, are evaluated according to their mechanistic effects, technological maturity, structural control, and demands for energy, reagents, water, solvents, effluent treatment, and capital. Across these routes, gelation and aging emerge as critical transfer stages through which feedstock composition is translated into network connectivity, pore architecture, shrinkage behavior, and ultimately functional performance. Evidence from secondary-source aerogels further shows that properly controlled waste-derived systems can attain BET surface areas of approximately 350–500 m² g⁻¹, within the textural range of many alkoxide-derived materials, indicating that feedstock variability, impurity management, and process control are more important constraints than an inherently lower performance ceiling. On this basis, this review proposes a minimum evidence framework comprising feedstock traceability, intermediate-speciation and colloidal characterization, silicon mass balance, gelation and aging metrics, application-specific qualification criteria, performance-normalized life cycle and techno-economic assessment, process analytical control, and staged pilot validation. Collectively, these principles provide a mechanistically grounded basis for moving sustainable silica synthesis beyond isolated proof-of-concept demonstrations toward reproducible, scalable, application-matched, and commercially credible manufacturing platforms. Full article

The construction sector is a complex industry whose growth and development are closely associated with overall economic expansion and the circular economy. Within this sector, Building Energy Simulation (BES) is widely employed to evaluate and compare the energy performance of proposed office buildings under both baseline conditions and with alternative heating, ventilation, and air-conditioning (HVAC) and domestic hot water (DHW) system configurations. The primary objective of this research was to conduct an energy performance assessment of administrative buildings located in Bratislava, Slovakia. A progressive methodology based on dynamic heat transfer simulation algorithms was applied to evaluate five alternative scenarios (C1–C5). Building performance and heat flow behavior were modeled and analyzed using DesignBuilder software (Version 7). The simulation results revealed that Scenario C5 represents the most effective solution for both administrative building A and administrative building B. From an economic standpoint, Scenario C5 also achieved the lowest energy costs when the DD3 electricity tariff was applied. The DD3 tariff is a dual-rate electricity pricing scheme intended for consumers with higher levels of electricity consumption during off-peak (low-tariff) periods. The findings indicate that a high level of energy sustainability in office buildings can be achieved through the effective implementation of optimized HVAC and DHW systems. Moreover, the integration of energy-efficiency measures contributes to enhanced economic performance by reducing overall energy consumption and associated operating costs. Full article

Absorbent pads are important materials for regulating exudate and local microenvironments in the packaging of high-moisture perishable foods. However, conventional absorbent pads often suffer from limited functionality, insufficient liquid retention, and a lack of active responsiveness. Hydrogels and aerogels, with tunable three-dimensional polymer networks, provide an important material basis for the design of new functional absorbent pads. This review focuses on the relationships among structure, function, and application, and compares hydrogels and aerogels in terms of network composition, crosslinking strategies, water absorption and retention mechanisms, and active compound loading and release behaviors. Structural design strategies, including multilayer structures, Janus structures, gradient pore structures, and micro/nano-reinforcement, are also summarized. On this basis, recent applications of hydrogel- and aerogel-based absorbent pads in the packaging of meat, aquatic products, fruits, vegetables, and edible fungi are discussed. Finally, the key challenges facing gel-based absorbent pads are analyzed, including adaptation to real food systems, release regulation, food-contact safety, and industrial-scale production. This review establishes a structure–function–application framework for gel-based absorbent pads and offers insights for designing sustainable active and intelligent food packaging. Full article

Journaling can support mental health and self-reflection, but traditional journaling requires users to act simultaneously as reflector, facilitator, and recorder, which may increase cognitive load and potentially hinder sustained practice or contribute to rumination. This study proposes the Reflective Conversational Journal (RCJ), an AI-based system in which AI supports facilitation and recording while users focus on reflection. Grounded in cognitive load theory, Rogers’ person-centered counseling principles, and Socratic questioning, RCJ was designed around three principles: contextual connectivity, structured recording, and empathy and questioning. A prototype integrating an AI agent, a template engine, and a client application was developed as a context-aware human–AI interaction system. Four experts in journaling and psychological counseling evaluated RCJ over one week and completed a post-use evaluation comprising Likert-scale items and open-ended questions. The mean score across the nine design-validity and implementation-fidelity items was 4.67/5 (SD = 0.48). Experts perceived contextual linking as useful for recognizing behavioral patterns and automatic structuring as helpful for reducing recording burden. However, limited depth in questions and interaction fatigue from frequent questioning were identified as areas for improvement. The findings provide preliminary evidence of design validity and implementation fidelity rather than objective evidence of cognitive-load reduction or clinical effectiveness. RCJ operationalizes a complementary human–AI role structure in which AI supports facilitation and recording while the user retains the reflector role. Full article

Nanomedicine has advanced cancer theranostics via targeted delivery and phototherapy, yet many high-performance systems rely on inorganic or metal-intensive materials synthesized through energy-demanding routes, raising concerns about biocompatibility, environmental accumulation, and sustainability. This review re-evaluates polypyrrole (PPy)-based nanomedicines from a green chemistry perspective, shifting focus from performance-centric optimization to sustainability-guided design. PPy, an organic conductive polymer with near-infrared photothermal activity and structural tunability, offers a promising platform. However, pristine PPy suffers from limited functionality, poor biodegradability, and insufficient reactive oxygen species (ROS) generation. Reported FeCl₃-, CuCl₂-, and Fe²⁺/H₂O₂-mediated routes are compared to examine formulation-specific relationships among synthesis conditions, polymer characteristics, redox behavior, ROS-related function, and process burdens. Because the underlying studies differ in composition, processing, purification, and assay conditions, these comparisons are used to identify evidence-supported trade-offs and data gaps rather than to establish a universal causal hierarchy. Green strategies are critically assessed, including one-step carboxylated copolymerization for backbone degradability and metal–polyphenol networks for catalytic ROS amplification. To organize the heterogeneous evidence, this review introduces a PPy-specific dual-axis evidence map that considers process-related sustainability alongside biofunctional performance. This qualitative tool is intended to identify trade-offs and evidence gaps rather than provide a validated sustainability score. Full article

Purpose: This study investigates the structural pathways driving the startup potential of Generation Z students in Romania’s post-transition economy. It examines the sequential relationship between Entrepreneurial Mindset (EM), Entrepreneurial Intentions (EIs), and Entrepreneurial Behavior (EB), focusing on the mediating role of intentions in bridging the gap between cognition and action. Design/methodology/approach: Using a quantitative explanatory design, data were collected through a two-stage hybrid framework from a sample of 215 Romanian business students associated with the Hackathon Innovation Labs (HILs), selected via a non-probability purposive sampling method. Hypotheses were tested using Structural Equation Modeling (SEM) with maximum likelihood estimation, supported by Confirmatory Factor Analysis (CFA) to ensure statistical rigor. Findings: Results confirm that EM is a robust predictor of EI, which significantly drives EB, explaining 45.2% of its variance. The findings highlight that intentions fully mediate the relationship, suggesting that a growth-oriented mindset turns into firm intentions to overcome institutional and cultural barriers. Originality: This research applies a rigorous SEM framework to a cohort of digital natives in an underrepresented Eastern European emerging market. It integrates mindset as a foundational cognitive precursor and provides empirical evidence of the sequential path to entrepreneurial behavior. Research limitations/implications: The study is limited by its sample size and geographic focus on Romanian business students. Future longitudinal research should explore external contingency factors, such as access to capital and ecosystem support, to validate model generalizability. Practical and social implications: Higher education should shift toward experiential programs like HILs, embedding credit-bearing hackathons and micro-credentials to foster an entrepreneurial mindset. Socially, sustaining this momentum with structured mentorship bridges the intention–action gap, transforming Gen Z’s digital potential into tangible economic value for the post-transition ecosystem. Full article

Smart city initiatives increasingly claim to be citizen-centric, yet governance frameworks persistently conflate two analytically distinct concepts, citizen participation and citizen engagement, in ways that undermine the design and evaluation of civic involvement mechanisms. This conceptual ambiguity represents a structural problem in the field, not a transitional oversight, and carries direct consequences for how urban managers design governance instruments and measure their effectiveness. This study systematically examines the scope, definition, and operationalization of both concepts in smart city research through a Systematic Literature Review (SLR) following the SPAR-4-SLR protocol. A corpus of 43 peer-reviewed articles published between 2011 and 2025, retrieved from Scopus and Web of Science, was subjected to qualitative content analysis using a structured coding framework. Findings reveal that 53% of reviewed studies use participation and engagement interchangeably, a pattern that remains stable across all publication periods, confirming the structural rather than incidental nature of the ambiguity. Only 26% of articles establish a rigorous conceptual distinction and operationalize both terms through distinct analytical frameworks. The review further identifies a critical mechanism design gap: 30% of articles report no engagement mechanism whatsoever, and only 23% report outcomes with verifiable indicators. Based on these findings, this study proposes a conceptual framework that explicitly distinguishes participation, as a behavioral, often episodic act, from engagement, as a sustained, intrinsically motivated process characterized by genuine influence over governance outcomes. The framework offers researchers a theoretically grounded basis for construct differentiation and provides urban managers with actionable criteria for designing governance mechanisms that move beyond symbolic consultation toward authentic co-creation. Implications for digital governance research and smart city policy are discussed, with particular attention to underrepresented contexts in the Global South. Full article

Natural biological materials achieve synergistic strengthening and toughening through soft–stiff dual-phase architectures, inspiring artificial composites. Despite extensive studies on individual bio-inspired designs, systematic comparative investigations under fully unified experimental conditions remain limited. Here, five representative bio-inspired composite structures (brick–mud, cross-lamellar, interlock, overlap, and concentric) are fabricated via 3D printing and compared under quasi-static three-point bending. Key mechanical parameters—including flexural modulus, flexural strength, crack-initiation displacement, effective fracture displacement, total energy absorption, and post-peak energy dissipation ratio—are derived from force–displacement curves, complemented by high-resolution imaging of crack paths, crack front morphologies, and fracture surfaces. The concentric structure exhibits the highest flexural modulus and flexural strength, yet fails catastrophically with only a 9.95% post-peak energy dissipation ratio. The brick–mud and cross-lamellar structures achieve the highest post-peak energy dissipation ratios (27.69% and 27.42%, respectively), which may be attributed to crack deflection and interfacial debonding, yet at the cost of low flexural strength. The interlock structure, apparently lacking effective deflecting interfaces, shows straight-through propagation and brittle behavior. In contrast, the overlap structure appears to benefit from sustained crack deflection along inclined interfaces, thereby providing a balanced combination of high flexural strength, large deformability, and moderate energy absorption, demonstrating the best overall mechanical performance. Full article

Future foods are driving an urgent need for sustainable and functional protein resources, and synthetic biology is emerging as a powerful platform to produce such proteins efficiently. Here, we designed a yeast protein (YP)–sanxan composite hydrogel obtained. The introduction of YP significantly improved thermal stability (by 5–15 °C) and ensured polymer compatibility. Rheological analysis indicated a frequency-dependent weak gel (tan δ = 0.1–0.3), making it suitable for safe swallowing. The material exhibited Type III nonlinear viscoelastic behavior, characterized by inter-cycle strain softening and a weak overshoot in G″, with Lissajous curves revealing a strain-induced transition from solid-like to fluid-like behavior. Crucially, YP-reinforced gels (5–20%) exhibited higher elastic moduli, indicating that the incorporation of YP strengthened the gel network and increased its structural rigidity, as further confirmed by Strain Sweep. With its tunable rheology and superior thermal stability, this hydrogel holds great potential for functional foods, 3D food printing, delivery systems, and biomedical scaffolds. Full article