Search Results (309)

Traditional microwave-absorbing metasurfaces struggle to integrate optical transparency with ultra-wideband and high-efficiency microwave absorption, severely limiting their deployment in optoelectronics-compatible electromagnetic protection. To address this constraint, we propose a transparent ultra-wideband microwave-absorbing metasurface based on multilayered indium tin oxide (ITO) films. The unit cell is constructed using a multilayered PMMA dielectric configuration, where ITO conductive layers are patterned as a top square patch, middle square rings, and a continuous bottom film. Full-wave parametric optimization, combined with multilayer resonant coupling, effectively extends the absorption bandwidth. We elucidate the underlying broadband absorption mechanism by analyzing electromagnetic field and surface current distributions at typical resonant frequencies. Furthermore, we systematically investigate the impacts of ITO sheet resistance, incident angle, and polarization state on absorption performance. A 6 × 6 array prototype is fabricated and experimentally characterized in a microwave anechoic chamber. The measured results demonstrate that the proposed metasurface achieves an absorptance exceeding 90% across 9.2–40.2 GHz, delivering a fractional bandwidth of 125.5%. The experimental responses are in good agreement with numerical simulations, and the fabricated prototype retains good optical transparency. Benefiting from the synergistic integration of ultra-wideband microwave absorption and superior optical transmissivity, this multilayer stacked metasurface offers a promising strategy for advanced optoelectronics-compatible stealth and transparent electromagnetic shielding applications. Full article

This perspective consolidates recent advances that position plasma and metamaterials as a unified metasystem for next-generation space micropropulsion systems. The need for new approaches arises because advanced small form-factor satellites and propulsion systems face physical and technological limits of conventional methods, including restricted scalability, limited electromagnetic control, and insufficient efficiency for complex and long-duration missions. These causes motivate the implementation of concepts based on metamaterials, plasma-based subsystems used in unconventional ways, and engineered ionized media. The paper integrates three complementary domains: plasma-enabled fabrication of complex metamaterials, engineered plasma–metamaterial interaction for controlled electromagnetic environments, and structured plasmas functioning as metamaterials with tunable effective properties. Emerging examples include metasurface-assisted waveguides for compact plasma sources, plasma-induced transparency platforms, machine learning-optimized metamaterial absorbers, and inverse-designed plasma metamaterials. Advances in plasma-based additive manufacturing and hierarchical material synthesis further expand the design space for multifunctional architectures, enabling adaptive, efficient and miniaturized propulsion concepts for CubeSat-class and small-satellite systems. Full article

Yb³⁺-containing glasses and glass-ceramics are attractive photonic materials because Yb³⁺ can act simultaneously as a near-infrared absorber, an energy-transfer sensitizer, a luminescent center, and a composition-dependent modifier of glass structure and crystallization. This brief review focuses on crystallization from parent glasses to glass-ceramics and examines glass-network chemistry, local Yb³⁺ coordination, phase separation, viscosity, heating rate, treatment temperature, holding time control nucleation, crystal growth, phase selection, rare-earth partitioning, transparency, and optical performance. Representative oxyfluoride, phosphate, oxyapatite, borosilicate, and aluminosilicate systems are compared using thermal analysis, X-ray diffraction, electron microscopy, vibrational spectroscopy, and optical spectroscopy. The available data show that Yb₂O₃ or YbF₃ does not have a universal effect on crystallization: low concentrations can promote fluoride-rich clustering or lower the apparent crystallization barrier, whereas higher concentrations can increase packing density, stabilize the residual glass, change the competitive phase assemblage, or suppress crystallization. Crystallization-enhanced luminescence is most consistently obtained when Yb³⁺ and the activator partition into low-phonon-energy nanocrystals while crystal size and refractive-index mismatch remain sufficiently small to preserve transparency. This review also identifies major reporting gaps, including limited quantification of crystalline fraction, partition coefficients, luminescence lifetime, quantum efficiency, and long-term thermal stability. Practical design guidelines and unresolved questions are proposed to support the rational development of transparent Yb³⁺-containing glass-ceramics for lasers, sensing, optical amplification, and related photonic applications. Full article

Transparent conducting oxides and electron transport layers are central to optoelectronic devices, yet their interfacial electronic behavior remains strongly dependent on substrate chemistry, defect states, and surface potential alignment. Here, we compare ITO and FTO transparent electrodes coated with ZnO and TiO₂, combining ab initio simulations, surface potential mapping, Hall effect measurements, sheet resistance, microscopy, and optical spectroscopy. Density functional calculations show that both ITO and FTO behave as degenerately doped n-type transparent conducting oxides, but with distinct work functions, surface dipoles, and donor-state distributions, leading to different interfacial charge-transfer tendencies. ZnO- and TiO₂-coated substrates display markedly different temperature-dependent transport, including resistance hysteresis and carrier-type switching, with FTO-based heterojunctions showing more clearly defined transitions due to the greater thermal stability of FTO. Scanning Kelvin probe (SKP) measurements reveal that ZnO more effectively accepts electrons from ITO or FTO, whereas TiO₂ shows weaker electron accumulation and more resistive interfacial behavior. Optical measurements and HSE06-based simulations confirm that TiO₂ behaves as a wider-gap ultraviolet absorber, while ZnO exhibits a lower-energy absorption onset, with real spectra additionally shaped by substrate, thickness, scattering, and defect contributions. The results show that transparent conducting oxide substrates are active electronic participants, not passive supports, in ZnO- and TiO₂-based optoelectronic interfaces. Full article

Breeding programs often adopt technologies before identifying the process that most limits genetic progress. This narrative review presents a bottleneck-first framework for annual self-pollinated crop breeding. It separates the diagnosis of a deficient pipeline domain from assessment of whether a specific intervention is actionable under uncertainty, capacity, and diversity constraints. Five domains are considered: usable variation, information for selection, biological progression and fixation, multi-environment validation, and delivery. Mandatory product gates and dependencies among domains determine priority. An intervention is actionable only when its lower uncertainty bound meets a predeclared minimum useful effect, downstream resources can absorb the added output, and diversity safeguards remain within declared limits. Three published cases provide retrospective stress tests: wheat high-throughput phenotyping, wheat pre-breeding, and SUBMERGENCE1 rice. Five additional cases examine realized gain, rapid generation advance, perennial selection, autotetraploid prediction, and promoter editing. A worked cereal example shows how capacity and diversity gates can reverse a technology-first priority. The framework complements rather than replaces selection indices, optimal contribution methods, genomic prediction, and breeding-scheme simulation. Its contribution is a transparent sequence for diagnosis, intervention testing, prioritization, and re-diagnosis. A prospective comparison with current breeding practice is still required. Full article

To address the bottlenecks of conventional resonant sound-absorbing structures—namely, fixed frequency bands, single functionality, and inapplicability to light-limited spaces—this paper designs and fabricates a composite-perforated Janus acoustic metamaterial using transparent SLA resin. By integrating acoustic impedance theory, parametric finite-element simulations, and impedance-tube experiments, we systematically investigate the sound absorption mechanisms under forward and reverse incidences, as well as the regulatory effects of aperture diameters and spacing on both sides. Results demonstrate that under forward conventional perforation incidence, the structure achieves near-unity low-frequency narrowband absorption at 322 Hz, with coefficients exceeding 0.8 across 308–337 Hz. Under reverse micro-perforated incidence, the absorption peak shifts to 658 Hz with a substantially broader effective band, maintaining coefficients above 0.8 from 611 to 710 Hz. The close agreement among simulations, theory, and experiments validates the reliability of our numerical models. Parametric studies reveal that the front-side perforations primarily tune the Helmholtz resonance frequency with marginal impact on peak magnitude, whereas the rear-side micro-perforations exhibit high sensitivity to aperture size, enabling independent and flexible tuning of absorption bands via bilateral geometric decoupling. By integrating two distinct absorption mechanisms within a single unit cell, this Janus architecture overcomes the limitations of narrowband low-frequency performance and functional singularity. Coupled with its optical transparency, it offers a novel noise-control solution for light-transmitting equipment and industrial pipelines, while providing a valuable reference for the design of multifunctional asymmetric acoustic metamaterials. Full article

Cadmium sulfide has been widely used as a conventional n-type window/buffer layer or heterojunction partner in several p-type thin-film solar cells, including CdTe/CdSeTe-, chalcopyrite-, kesterite-, antimony chalcogenide-, tin sulfide- and iron pyrite-based devices. Its success is related to its ability to form suitable heterojunctions, partially passivate absorber surfaces and provide favorable electronic selectivity. However, the parasitic absorption associated with the relatively narrow band gap of CdS, the toxicity and waste-management issues related to cadmium-containing auxiliary layers and the need for improved band alignment have motivated extensive research on CdS-free window and buffer layers. This review summarizes the main efforts devoted to replacing CdS in thin-film solar cells based on absorbers such as CdTe/CdSeTe, CIS, CIGS, CZTS, CZTSe, CZTSSe, Sb₂S₃, Sb₂Se₃, Sb₂(S,Se)₃, SnS and FeS₂. The most investigated alternative materials, including Zn(O,S), ZnS, In₂S₃, ZnMgO, ZnSnO, TiO₂, SnO₂ and SnS₂, are discussed with emphasis on their optical properties, band alignment, interface quality, deposition methods and impact on device performance. The analysis highlights that CdS replacement cannot be treated as a universal material substitution problem. Instead, each absorber and device architecture requires a specific front-interface design, where chemical compatibility, conduction band offset, defect passivation, optical transparency and process-induced interfacial modifications play a decisive role. CdS-free approaches are relatively mature for CdTe/CdSeTe- and CIGS-based solar cells, whereas kesterite absorbers, antimony chalcogenides and SnS still require further interface engineering. In FeS₂, by contrast, buffer-layer substitution remains secondary to the control of intrinsic surface and bulk electronic defects. This review provides a concise comparison of the most relevant CdS-free front/window materials and identifies key challenges for the future design of sustainable thin-film solar cells. Full article

Environmental, social, and governance (ESG) ratings are now central to how firms’ sustainability is assessed, yet leading providers disagree sharply, injecting measurement error and uncertainty into any rating-based decision. This study proposes and applies a transparent, fully reproducible alternative for the environmental pillar: an ordinal, sector-based carbon-exposure measure constructed solely from firms’ publicly observable industry classifications, free of vendor scoring choices and reconstructable at zero cost. The measure captures structural, between-sector carbon exposure; it is not a firm-level environmental-performance score and does not use reported emissions. Using 3067 firm-year observations on 1049 listed non-financial firms that carry an observed sector classification across six developed markets (the United States, the United Kingdom, Australia, France, Italy, and Spain) over fiscal 2021–2025 (with a small number of early fiscal-2026 period-ends), we assess the measure’s informativeness by estimating its association with accounting profitability in high-dimensional fixed-effects models. Descriptively, more carbon-intensive sectors are less profitable (a monotone brown tilt), but this association is not robust: once firm controls and country-by-year fixed effects are absorbed, carbon exposure is not significantly related to return on assets, return on equity, or net margin, and there is no evidence of a concave (inverted-U) pattern. The measure does recover a real operating difference, higher asset turnover among carbon-intensive sectors, but this is offset by margins and does not translate into a profitability premium. A within-firm design detects no differential effect of mandatory non-financial reporting. The contribution is a transparent, rule-based environmental measure that sidesteps rating divergence; the honestly reported null on profitability cautions that apparent effects are sensitive to sample construction and sectoral composition, and positions the measure as a complement to, rather than a substitute for, proprietary ESG ratings. Full article

Recurrent and increasingly severe flooding along the Wabi Shabelle River—displacing approximately 184,000 people from Beledweyne, central Somalia, in the 2020 Gu season alone—has made in situ reconstruction untenable and planned resettlement a central adaptation option. Site selection in this agropastoral context must simultaneously avoid the riparian flood corridor and preserve access to the river as the dominant livelihood resource. We develop a transparent, reproducible GIS-based Analytic Hierarchy Process–Weighted Linear Combination (AHP–WLC) framework over a 30 × 30 km region of interest at 30 m resolution. A hard safety mask (Height Above Nearest Drainage > 5 m and slope < 5°) is combined with six normalised criteria, including a non-monotonic, piecewise river-livelihood score, using literature-anchored AHP weights (consistency ratio CR = 0.004). Seven initial criteria were pre-screened with Pearson, Spearman and Variance Inflation Factor diagnostics (maximum |r| = 0.52, maximum VIF = 1.44), removing a perfectly collinear services-distance layer before weighting. Robustness was confirmed by a ±10% one-at-a-time sensitivity analysis with targeted river-weight and HAND-threshold tests, all criteria remaining very robust (|Δ| < 5%). The composite identifies 12,723 ha (14.3%) as highly suitable, resolving into 113 operationally meaningful candidate sites (≥5 ha; 95.6% of the highly suitable area). Candidate areas sufficient to absorb the 2020 displacement land demand (552–1104 ha) lie within 6 km of the city centre. The framework offers an operational, defensible foundation for resettlement planning in flood-exposed agropastoral cities of the Horn of Africa. Full article

As China’s new energy vehicle (NEV) industry shifts from scale expansion to sustainable competition, enterprise risk is increasingly shaped by price pressure, innovation investment, operational efficiency, and cash-flow quality. Conventional financial early warning models based on static accounting ratios are limited in capturing how such risks emerge and transmit within NEV business ecosystems. This study develops an AI-driven risk governance framework that combines a digital twin-inspired state representation, interpretable machine learning, Shapley additive explanations, and competitive scenario simulation. Using annual data from 2021 to 2025 for twelve listed Chinese NEV automakers, we construct forty-eight enterprise-year observations and predict next-period high-risk status from current-period financial, operational, and competitive state vectors. Logistic regression is used as a transparent benchmark, while XGBoost serves as the main nonlinear learner. The results show that NEV risk identification requires the joint consideration of profitability, R&D intensity, cash-flow quality, asset utilisation, and liquidity, rather than reliance on a single accounting indicator. Logistic regression provides stronger temporal stability, whereas XGBoost achieves higher recall and area under the receiver operating characteristic curve in cross-validation. SHAP results identify return on assets, R&D intensity, operating cash-flow ratio, fixed asset turnover, and current ratio as the leading contributors to model predictions. Scenario simulations reveal asymmetric resilience: low-risk firms can absorb moderate competitive shocks, while high-risk firms remain locked in elevated risk states. This study provides a practical decision-support framework for identifying risk drivers, evaluating competitive shocks, and improving risk governance in sustainable NEV business ecosystems. Full article

Developing advanced bioinspired photoprotective barrier from marine resources represents a critical frontier of bioprocessing. This study established a rational design and implementation of effective photoprotective surface-coating eumelanin from ink of an Indian squid (Uroteuthis duvaucelii). The Central Composite Design was developed to optimize extraction and functionalization parameters of eumelanin on quartz substrates, strategically developing the matrix for peak optical attenuation within the potential Far-UVC window (220 nm). Translational photoprotective efficacy of the surface, as well as finished eumelanin on quartz surface, was validated by subjecting them to a challenging macro-level biological assay using a hospital-grade 254 nm ultraviolet germicidal source (125 µWcm⁻²). Quantitative physical dosimetry established that the squid eumelanin coating (A254 = 1.00) reduced internal transmittance to approximately 10%, successfully dampening the incident fluence from 0.225 J cm⁻² down to a heavily attenuated 0.0225 J cm⁻² at the biological sample plane. While unshielded control indicator microbial strains suffered complete lethal inactivation, the eumelanin barrier maintained exceptional cell viability, yielding biological shielding efficiencies of 98% for Bacillus subtilis, 96% for Staphylococcus aureus, and 92% for Escherichia coli. Characteristic features from FE-SEM, FTIR, and XRD analysis established that this superior photoprotective property is governed by the extensively conjugated, π-π-stacked indolic architecture possessing a characteristic 3.4 Å interlayer d-spacing, which facilitates rapid, non-radiative energy dissipation. This work establishes an effective framework for translating squid biomass into high-value, transparent optical barriers, providing a potential sustainable alternative to synthetic ultraviolet absorbers. Full article

The skin is the largest organ of the human body and, due to its direct contact with the external environment, is one of the most vulnerable tissues. Traditional medical bandages and gauze exhibit limited efficacy in wound management, often neglecting the control of wound inflammation and the promotion of skin regeneration. Hydrogels, as an emerging material, possess appropriate swelling capacity, oxygen permeability, and the ability to absorb wound exudates, thereby facilitating wound healing, making them an ideal choice for functional applications in skin tissue engineering. In this study, dual-treated balsa wood (BWSM) was used as the hydrogel substrate, with polyvinyl alcohol (PVA), chitosan (CS), and zinc gluconate (ZnG) used as the primary raw materials. The BWSM/PVA/CS/ZnG hydrogel was prepared via gamma-ray irradiation. Balsa wood treated with alkaline solutions, hydrogen peroxide solutions, and microwave treatment processing exhibited enhanced transparency, increased porosity, improved thermal stability and swelling rates, while retaining adequate mechanical strength. Gamma-ray irradiation of the BWSM/PVA/CS/ZnG hydrogel wound dressing demonstrated sustained drug release and antibacterial efficacy through release and antimicrobial tests. Animal experiments showed that the BWSM/PVA/CS/ZnG composite hydrogel promoted wound healing in mice and effectively prevented scar formation. The aforementioned results demonstrate that the PVA/CS/ZnG composite hydrogel loaded with balsa wood exhibits durable antibacterial properties and high mechanical strength and promotes wound healing, making it suitable for applications in biomedical materials such as wound dressings. Full article

Gel-based materials are emerging as lightweight, mechanically compliant, and electromagnetically tunable platforms for next-generation antennas, electromagnetic interference (EMI) shields, microwave absorbers, and radomes. This review summarizes recent progress in hydrogel-, aerogel-, ionogel-, organohydrogel-, and xerogel-based electromagnetic materials, with emphasis on how network structure, pore architecture, solvent phase, and functional fillers regulate permittivity, conductivity, impedance matching, and attenuation. The device-level roles of gels are discussed in miniaturized and reconfigurable antennas, absorption-dominated shielding systems, broadband microwave absorbers, high-temperature wave-transparent radomes, and metamaterial, energy-harvesting, and bioelectronic systems. Particular attention is paid to the mechanisms of dipolar relaxation, ionic conduction, interfacial polarization, conduction loss, magnetic loss, and multiple scattering. Finally, key challenges are identified, including hydrogel dehydration and freezing, aerogel fragility, ionogel cost and leakage, limited long-term reliability, and the lack of standardized performance metrics. Future directions toward durable, scalable, multifunctional, and device-integrated gel-based electromagnetic materials are proposed. Full article

Offshore wind is expanding globally, driven by energy security and decarbonization goals. Brazil’s world-class potential for this resource is challenged by its unique context: an already clean electricity matrix and abundant, low-cost onshore alternatives, which reduce the immediate urgency for deployment. This paper starts with a global offshore wind market analysis, understanding why the main countries pursue this technology, in contrast with Brazil’s already high share of renewable generation. The following examination focuses on Brazil’s recently approved new offshore wind framework and the governance-related issues, revealing that the legislative process was distorted by unrelated riders mandating costly, non-competitive energy procurement. These riders threatened to absorb future market growth, undermining competition and jeopardizing the emergence of the entire offshore wind industry. While presidential vetoes of these riders were essential to preserve this opportunity, remaining market distortions still favor mature technologies. The study concludes that Brazil’s primary barrier to offshore wind is not technical or resource-based but institutional: the need for stable, transparent governance to foster a truly competitive and predictable policy environment. Full article

Light-converting polymer coatings and films are emerging passive photonic materials for spectral engineering in sustainable and protected agriculture. By absorbing ultraviolet or weakly used spectral components and re-emitting in visible bands that overlap with photosynthetic pigments and plant photoreceptor action regions, these materials can modify the radiation environment without additional electrical energy input. This critical narrative review analyses light-converting polymer films and coatings from a materials and coatings perspective, with emphasis on photophysical mechanisms, polymer matrices, luminophore families, coating fabrication routes, optical transparency, photoluminescence, aggregation phenomena, photostability and scalability. The photobiological background is included as a concise framework that justifies the spectral targets of the conversion process. Rare-earth complexes, inorganic phosphors, quantum dots, aggregation-induced-emission systems and organic dyes are compared as candidate luminophores. Particular attention is devoted to the general challenges associated with organic luminescent coatings, including dispersion, aggregation, optical transparency, photostability, and scalability. A PMMA/PDI coating system is discussed only as an illustrative case study demonstrating these broader materials-design considerations. Extrusion, solution casting, spin-coating, dip-coating and sol–gel processing are evaluated as fabrication strategies for laboratory and large-area greenhouse applications. The work concludes by identifying the main gaps that must be addressed before practical deployment: quantitative UV–Vis and photoluminescence characterization, absolute quantum yield, haze and scattering, thickness and morphology mapping, accelerated UV aging, weathering resistance, toxicity assessment and crop-specific validation. Full article