Search Results (854)

The transition from conventional synchronous generators to inverter-based power systems has introduced significant challenges in stability, reliability, and protection coordination. Grid-forming inverters (GFMs) have emerged as a promising solution by emulating inertia and voltage regulation functions while enabling grid-supportive operation in weak or islanded networks. This study presents a structured qualitative review of the recent literature on GFM technologies. The selection process focused on control strategies, advanced semiconductor materials, protection frameworks, and cyber–physical security considerations. A thematic synthesis and comparative analysis were conducted to identify emerging trends and technical gaps. Among established approaches, virtual synchronous machine (VSM) and droop control remain widely adopted. More advanced strategies, including virtual oscillator control (VOC) and model predictive control (MPC), demonstrate improved dynamic performance in weak-grid conditions. Advances in semiconductor technologies, particularly Silicon Carbide (SiC) and Gallium Nitride (GaN), enable faster switching, higher efficiency, and enhanced thermal performance. The findings indicate a growing shift toward decentralized control architectures, fault-resilient converter topologies, and integrated protection–control co-design. Emerging solutions include grid-forming synchronization techniques that replace conventional phase-locked loop (PLL) structures, intrusion-tolerant inverter firmware with embedded anomaly detection, and predictive fault-clearing schemes tailored for low-inertia networks. Despite these advancements, several research gaps remain. These include limited large-scale validation of VOC and MPC strategies under high renewable penetration, insufficient interoperability metrics for legacy system integration, and a lack of standardized cybersecurity benchmarks across platforms. Future research should prioritize real-time experimental validation, robust protection co-design methodologies, and the development of regulatory and dynamic performance standards tailored to inverter-dominated grids. Strengthening protection coordination and interoperability frameworks will be essential to ensure the secure and stable deployment of GFMs in modern power systems. Full article

Photoelectrochemical (PEC) water splitting offers a sustainable route for solar-to-hydrogen conversion, yet its large-scale deployment is often hindered by energy-intensive and costly fabrication processes for semiconductor photoelectrodes. Electrodeposition provides an attractive alternative owing to its solution-based, low-temperature, and scalable nature; however, the relationship between electrochemical deposition parameters and photoelectrode functionality remains insufficiently understood. Herein, we systematically investigate system-level control in electrodeposition for photoelectrode synthesis using BiVO₄ photoanodes and CuO/Cu₂O photocathodes as model systems. By modulating deposition potential, current density, and electrical control modes, we elucidate how interfacial ion dynamics and growth kinetics govern film morphology, phase evolution, and PEC performance. DC electrodeposition establishes a baseline structure–performance relationship governed by precursor concentration and current density, while pulsed operation enables decoupling of nucleation and growth, leading to refined nanostructures and enhanced photocurrent responses. Further incorporation of reverse-pulsed potentials provides dynamic interfacial reset, enabling precise control over porosity and grain connectivity. The optimized BiVO₄ photoanodes fabricated under tailored reverse-pulsed conditions exhibit improved photocurrent density compared to continuously deposited counterparts. The insights presented here provide practical guidelines for rationally engineering high-performance, scalable, and environmentally benign photoelectrodes for PEC water splitting. Full article

Phase change materials (PCMs) have emerged as a key enabler of high-performance, low-carbon buildings through latent heat-based thermal energy storage. This paper presents a systematic and critical synthesis of advances in PCM technologies for building applications published between 2022 and 2025, analyzing over 300 peer-reviewed studies to evaluate thermal performance, economic viability, environmental impact, and climate adaptability across three integration approaches: passive, active, and hybrid systems. The studies analyzed show that passive envelope integration employing macroencapsulated or form-stable PCMs in walls, roofs, and glazing is reported to deliver 15–45% energy savings with payback periods of 8–15 years, primarily through enhanced thermal inertia and indoor temperature stabilization. Active systems, which couple PCMs with HVAC, heat pumps, or air handling units, are found to achieve 20–40% energy reductions and shorter payback periods (3–8 years) by enabling load shifting, peak shaving, and improved coefficient of performance (COP). Hybrid configurations integrating passive and active strategies with AI-driven control demonstrate, in the literature, the highest potential, with reported energy savings of up to 50%, though they entail greater complexity and capital cost. The review further highlights material-level innovations, including ternary composite PCMs, bio-based alternatives, and nano-enhanced formulations that address intrinsic limitations such as low thermal conductivity (0.1–0.3 W/m·K for organics) and cycling instability. Despite significant progress, critical gaps persist in standardized testing protocols, long-term field validation, comprehensive lifecycle assessments, and real-world scalability, particularly in tropical and cold climates. By bridging material science, building physics, and energy system engineering, this work provides a forward-looking roadmap to accelerate the deployment of PCM-based solutions in the global decarbonization of the built environment. Full article

This review focuses on the use of metal–organic frameworks (MOFs) for environmental remediation through adsorption processes in both liquid and gas phases. Due to their high surface areas and chemical tunability, MOFs offer promising performance in adsorbing environmental pollutants compared to traditional materials. In this work, we discuss advanced synthesis techniques, including solvothermal, room temperature, and mechanochemical techniques, and how each technique influences the resulting MOF’s structural properties. Furthermore, we analyze the use of MOFs as adsorbents for CO₂ and volatile organic compounds (VOCs) in the gas phase, as well as their role in removing heavy metals, fluorides, dyes, and emerging pharmaceutical contaminants. Although MOFs possess intrinsic limitations, such as instability in the presence of water and challenges in cyclic regeneration, their combination with other materials has aimed to overcome these drawbacks by leveraging the best properties of each component in new hybrid materials. Finally, we evaluate various challenges, such as large-scale implementation, toxicity, and long-term stability, proposing sustainable solutions for environmental remediation. Full article

Volatile coordination compounds are widely used as precursors for the gas phase synthesis of functional materials. However, such complexes are still very rare for alkali metals, especially for heavy representatives of this family (potassium, rubidium, cesium) due to the tendency to form polymeric structures. This work is devoted to the exploration of a potassium hexafluoroacetylacetonate complex with 18-crown-6 ether, K(18C6)(hfac), as a unique volatile precursor with an isolated molecular structure. A convenient synthesis procedure was developed, and key structural features were identified including temperature-dependent effects. The thermal properties of the complex were studied via thermogravimetry and measurements of saturated vapor pressure using the Knudsen effusion method with mass spectrometric registration of the gas phase composition. Both from solution and the gas phase, the molecular films of K(18C6)(hfac) obtained exhibit a strictly (h00) orientation, where half of the surface cations have a coordination sphere accessible to supramolecular contacts. For the first time, the possibility of producing potassium-containing films from a fluorinated precursor by metal–organic chemical vapor deposition (MOCVD) has been demonstrated. With oxygen as the reactant gas, potassium fluoride forms and interacts with the silicon substrate, while introducing water vapor significantly reduces the fluorine content, suggesting its suitability for the preparation of oxide films. Full article

Amorphous calcium phosphate (ACP), a key calcium-phosphorus compound, has been widely applied in fields such as dentistry, orthopedics, and biomedicine. However, its potential for removing copper ions from aqueous solutions remains largely unexplored. In this study, sodium citrate-stabilized amorphous calcium phosphate (Cit-ACP) and its calcined derivatives at various temperatures were successfully synthesized as adsorbents for copper ions. The adsorption behavior of Cit-ACP was best described by the Langmuir isotherm, with kinetics following a pseudo-second-order model. Under conditions of pH 5.5 and an initial copper ion concentration of 200 mg/L, Cit-ACP exhibited a maximum adsorption capacity of 323.96 mg/g. Thermodynamic analysis confirmed that the adsorption process was spontaneous and endothermic. Comprehensive characterization via XRD, XPS, and zeta potential measurements before and after adsorption revealed a two-stage adsorption mechanism. At low initial copper concentrations, adsorption occurred predominantly through surface complexation between copper ions and sodium citrate molecules on Cit-ACP nanoparticles. At higher concentrations, the mechanism extended to include co-precipitation of copper ions with hydroxyl groups, which promoted the transformation of Cit-ACP into copper-substituted calcium phosphate phases, such as copper-containing hydroxyapatite. Owing to its straightforward synthesis, high adsorption capacity, and inherent biocompatibility, Cit-ACP presents a promising, cost-effective, and efficient adsorbent for the removal of copper ions from aqueous environments. Full article

The valorization of agro-industrial residues through fermentation processes represents a sustainable approach to producing high-value bioproducts, such as microbial organic acids and fermentation-derived anti-browning agents, including kojic acid and kojic acid-rich fermented extracts. In this study, melon waste (non-commercial-quality or damaged fruit) was evaluated as an alternative carbon source (whole fruit) for kojic acid (KA) production by Aspergillus oryzae (ATCC 10124) under submerged fermentation. The effects of process variables such as pH, temperature, and nitrogen and carbon availability on KA synthesis were analyzed, and biomass growth and product formation were described using logistic and Luedeking–Piret kinetic models. Under optimal conditions (pH 5.5, 36 °C, 2.5 g/L melon dry matter, 2.5 g/L yeast extract, 100 rpm), KA production reached 1.64 g/L at a final time of 120 h. Kinetic analysis showed moderate fungal growth (μ_max = 0.058 h⁻¹; X_max = 0.81 g/L), with KA formation following a mixed growth-associated pattern as described by the Luedeking–Piret model (α = 1.26 g KA/g X; β = 0.024 h⁻¹), indicating sustained production during the stationary phase. The KA-rich fermented extract was subsequently applied as an anti-browning treatment on spineless prickly pear (Opuntia ficus-indica) cladodes. Short immersion times (0.5–1.0 min) in a 2 g/L KA solution significantly preserved luminosity (L*) and limited total color change (ΔE ≤ 5) during 4 days of storage at 28 °C, compared with water-treated controls, which exhibited accelerated darkening (ΔE ≈ 9–15). Prolonged immersion times induced tissue damage and color deterioration, indicating an optimal exposure window. These results demonstrate the feasibility of valorizing melon waste to obtain a KA-rich extract and support its potential application as a natural anti-browning agent in fresh-cut vegetables within a circular agrifood framework. Full article

A microwave–hydrothermal (M-H) method was developed for synthesizing barium silicate from solutions of barium salts and sodium silicate. Advanced techniques (DTA, XRD, IR spectroscopy, SEM and TEM) were used to study the optical, granulometric, electrical and other functional characteristics of barium silicate. BaSiO₃ synthesized at 100 °C is an amorphous nano-sized powder (10–20 nm); however, the product synthesized at 240 °C has a crystalline structure (20–27 nm), whereas the crystalline phase of BaSiO₃ is typically obtained using known methods at temperatures above 400 °C (12–40 nm). During M-H synthesis, it was found that the structure formation mechanism and particle size of BaSiO₃ changed due to the peculiar features of microwave heating. The synthesized barium metasilicate exhibits a high diffuse reflectance coefficient of 92%. It is a wide-band-gap semiconductor with a band gap width of Eg = 4.1 eV. Both amorphous and crystalline phases of BaSiO₃ exhibit high photocatalytic activity in the UV range. This study shows that the developed M-H method enables the production of nano-sized powder and enhances the functional properties of barium silicate. Compared with conventional methods, the M-H method is more efficient due to reduced synthesis time and lower energy costs. Full article

Reliable multivariable control is critical for industrial sectors where processes exhibit severe nonlinearities and interactions. A Continuous Stirred Tank Reactor (CSTR) is a rigorous benchmark for testing control strategies addressing these complexities. This work first establishes a linear MIMO mathematical framework to define the specific structure of such interactive systems. Analysis via phase planes and steady-state analysis reveals low controllability, bistability, and strong coupling, leading to the collapse of traditional decoupled control schemes. To address these issues via multivariable control, we propose a centralized MIMO RST control structure synthesized via a Matrix Fraction Description (MFD) and the extended Bézout equation. Simulations for performance evaluation and comparison highlight the following key findings: (1) the centralized RST maintains stability and tracking precision in regions where decentralized RST loops fail; (2) it exhibits performance comparable to the Augmented State Pole Placement with Integral Action (ASPPIA) method and outperforms the standard Model-Based Predictive Control (MPC) baseline, particularly during critical equilibrium point transitions; and (3) it offers a robust yet computationally simple design that provides superior flexibility for pole placement, accommodating future identification-based models and adaptive tuning. These results validate our algebraic synthesis as a robust, computationally efficient solution for managing highly interactive nonlinear dynamics. Full article

Acidity is a primary factor leading to the deterioration of paper-based cultural heritage, and deacidification treatment is a crucial preventive conservation measure for extending their lifespan. Traditional deacidification techniques, such as the particle suspension method and vapor phase method, have limitations in terms of penetration uniformity, treatment efficacy, or safety. Nanoscale alkaline materials, represented by nano-calcium hydroxide and nano-magnesium hydroxide, offer an innovative solution with the potential to achieve more uniform, efficient, and long-lasting paper deacidification, owing to their high specific surface area, enhanced reactivity, and superior penetration capacity derived from the nanoscale dimension. It is important to note that the realized uniformity and depth of treatment are contingent upon substrate properties (e.g., fiber density, porosity) and application parameters. This paper provides a systematic review of the main types of nanomaterials applied in the deacidification of paper artifacts—including their synthesis and dispersion stabilization methods—application techniques (such as immersion and spraying) and performance evaluation systems (including pH value, alkaline reserve, and mechanical properties). Through comparative analysis and case studies, the advantages and current challenges of nano-deacidification technology are elaborated. Finally, future directions for nano-deacidification technology are discussed, particularly focusing on material optimization, standardized evaluation, and prospects for scalable application tailored to the practical needs of cultural heritage conservation. Full article

The synthesis of enantiomerically pure chiral β-nitroalcohols is a crucial objective in asymmetric catalysis. In order to efficiently obtain such chiral products, we developed a series of thermoresponsive, oxazoline–copper catalysts (Cu^II-PN_xFe_yO_z) via sequential reversible addition–fragmentation chain transfer (RAFT) polymerization. These catalysts can self-assemble in water into single-chain nanoparticles (SCNPs) with biomimetic behavior, in which intramolecular hydrophobic and metal-coordination interactions generate a confined hydrophobic cavity. Comprehensive characterization by FT-IR, TEM, DLS, CD, CA, and ICP analysis confirmed the nanostructure and composition. When applied to the aqueous-phase asymmetric Henry reaction between nitromethane and 4-nitrobenzaldehyde, the optimal catalyst (2.0 mol%) achieved a quantitative yield (96%) with excellent enantioselectivity (up to 99%) within 12 h. Furthermore, the thermosensitive poly(N-isopropylacrylamide, NIPAAm) block enabled facile catalyst recovery through temperature-induced precipitation above its lower critical solution temperature (LCST). This work presents an efficient and recyclable biomimetic catalytic system, offering a novel strategy for designing sustainable chiral catalysts for green organic synthesis. Full article

This work investigates the synthesis, thermodynamic phase stability and microstructural, mechanical and tribological behavior of the CrFeMoV alloy system and its Al-modified derivatives, CrFeMoV-Al2 and CrFeMoV-Al6, which belong to the family of high- and medium-entropy alloys. The studied systems were produced via Vacuum Arc Melting (VAM), followed by a comprehensive characterization. Thermodynamic and geometric phase-formation models were employed to predict the formation of BCC/Β2 solid solutions and the potential emergence of σ-type intermetallic compounds. An ML model was also employed to further predict elemental interactions and phase evolution. These predictions were experimentally confirmed via X-ray diffraction analysis, which verified the presence of a BCC matrix in all compositions, the presence of σ-phase precipitates whose volume fraction systematically reduced with Al inclusion and the gradual increase in the B2 phase with the increase in the Al content. Scanning electron microscopy and EDX analyses uncovered noticeable dendritic segregation, with Mo and Fe enrichment in dendrite cores and in interdendritic regions, respectively. Cr, V, and Al were more uniformly distributed. Mechanical property data derived by micro hardness testing demonstrated a high hardness of 816 HV for the base alloy, ascribed to σ-phase strengthening, followed by a progressive reduction in this value to 802 HV and 756 HV in Al-containing alloys due to the attenuation of σ-phase formation and the gradual increase in the B2 phase. Dry sliding wear results unveiled a positive correlation between wear resistance and hardness, confirming the beneficial role of intermetallic strengthening. Finally, nanoindentation tests shed light on the nanoscale mechanical response, confirming the trends observed at the microscale. Overall, the combination of thermodynamic modeling and experimental analysis provide a robust framework for understanding phase stability, microstructural evolution, and mechanical performance in Al-alloyed CrFeMoV high-entropy systems, while highlighting the potential of controlled Al additions to tailor microstructure and properties. Full article

Rapid urbanization and climate change have intensified flood risk and ecological degradation along urban riverfronts. Recent literature suggests that combining green and grey infrastructure can enhance resilience while delivering ecological and social co-benefits. This study analyzes and compares five riverfront projects in China and Spain, assessing how their tactic mixes operationalize three urban flood-resilience strategies—Resist, Delay, and Store/reuse—and how these mixes translate into ecological, social, and urban impacts. A six-phase framework was applied: (1) literature review; (2) case selection; (3) categorization of resilience strategies; (4) systematization and typification of tactics into green vs. grey infrastructure; (5) percentage analysis and qualitative matrices; and (6) comparative synthesis supported by an alluvial diagram. Across cases, Delay emerges as the structural backbone—via wetlands, terraces, vegetated buffers, and floodable spaces—while Resist is used selectively where exposure and erodibility require it. Store/reuse appears in targeted settings where operational capacity and water-quality standards enable circular use. The comparison highlights hybrid, safe-to-fail configurations that integrate public space, ecological restoration, and hydraulic performance. Effective urban riverfront resilience does not replace grey infrastructure but hybridizes it with nature-based solutions. Planning should prioritize Delay with green systems, add Resist where necessary, and enable Store/reuse when governance, operation and maintenance, and water quality permit, using iterative monitoring to adapt the green–grey mix over time. Full article

The growth of the Internet of Things (IoT) has increased the demand for low-cost nanostructured materials. Zinc tin oxide (ZTO) has been widely used as an alternative to current semiconductor technologies, but its production methods remain expensive. Combustion synthesis is a green, low-cost alternative that may allow us to reduce the complexity of ZTO production. In this work, zinc and tin-based nanostructures were produced through combustion synthesis using water and ethanol as solvents and different precursor solutions ratios (1:2, 1:1, and 2:1). The influence of ethylenediamine (EDA) on the crystallographic phase of 2:1 samples of both solvents and Ag doping on 2:1 ethanol samples was also studied. Samples produced with a 2:1 ratio presented a predominance of ZnO, while the 1:1 and 2:1 samples presented a mixture of ZnO, SnO₂, and ZnSnO₃. The use of EDA in the 2:1 ethanol and water samples led to the growth of ZnO after annealing at 600 °C. For the ZTO-Ag samples, X-ray diffraction (XRD) and Raman analysis also revealed the presence of ZnO after annealing at 600 °C. This work showed it is possible to produce ZTO nanostructures through solution combustion synthesis. Full article

This paper presents a method for dimensional synthesis of a pulse-type adjustable speed mechanical drive, realized through a Watt II six-bar linkage combined with an overrunning clutch. The goal is to achieve a transmission ratio that varies smoothly and linearly by adjusting the angle of a control lever, while meeting kinematic, geometric, and force constraints. The kinematic characteristics are derived analytically using vector-loop equations, enabling comparison with a predefined linear reference function. An optimization problem is formulated to minimize the maximum deviation between the actual and reference output angles across the entire operating interval. The solution employs a metaheuristic algorithm for global search followed by a local refinement phase. Three optimization scenarios are analyzed, each with different levels of design freedom regarding the parameters defining the linear reference function. The results demonstrate a clear trade-off between accuracy and functional tunability, highlighting the most effective balance for practical applications. This approach can be used for designing mechanical drives with adjustable speed features and can be applied to other complex linkage systems. Full article