Search Results (3,216)

A bidirectional controllable terahertz multifunctional device based on graphene and vanadium dioxide is proposed in this paper. By adjusting the phase transition characteristics of vanadium dioxide and the chemical potential of graphene, the bidirectional transmission of electromagnetic waves is regulated to achieve multiple functions. When vanadium dioxide is in its metallic state, the device exhibits circular dichroism at 5.65 THz for the forward left- and right-circularly polarized waves. For the backward-propagating electromagnetic waves, when the chemical potential of graphene is 1 eV and 0 eV, the device shows broadband absorption and broadband orthogonal polarization conversion, respectively. The relative bandwidths are 101.1% and 126.3%, respectively. When vanadium dioxide is in its insulating state, the device exhibits an obvious asymmetric transmission effect on left- and right-circularly polarized light at 1.66 THz and 3.1 THz. The proposed metasurface is expected to expand the application of terahertz technology and has broad prospects in the fields of 6G mobile communication, high-capacity information processing, environmental and food detection. Full article

Early-stage post-conflict regions must rebuild essential infrastructure while avoiding development pathways that create long-term environmental and institutional costs. This study examines how green reconstruction, policy sequencing, and sustainable regional competitiveness may co-evolve in Karabakh and Eastern Zangezur during 2025–2040. A scenario-based System Dynamics (SD) model developed in Vensim compares Baseline Reconstruction, Eco-Tourism Promotion, Green Investment, an Integrated Policy Mix, and Accelerated Reconstruction. The normalized simulations indicate that stand-alone interventions generate partial gains and trade-offs, whereas the full Integrated Policy Mix produces the most balanced outcome under its stated, more favourable policy settings. Eco-tourism promotion increases attractiveness and demand but may intensify carrying-capacity stress when services and environmental management lag; accelerated reconstruction can create institutional overload when implementation demands exceed absorptive capacity. A matched policy-intensity comparison does not show uniform mixed-package dominance over both stand-alone alternatives, so the full Integrated advantage cannot be interpreted as a pure coordination effect. An exploratory global uncertainty analysis preserves the original ranking under the specified perturbation design. The results are assumption-dependent policy experiments rather than empirically estimated forecasts and support conditional, phased, and capacity-sensitive reconstruction strategies. Full article

Converter slag and copper slag represent promising sources for ceramic materials, but their high total iron content leads to waste of iron resources and inferior ceramic performance. To address this issue, we propose a two-step utilization method for converter slag and copper slag, including iron extraction synergistic oxidation and ceramic fabrication for tailings. In this study, the effects of tailings content, sintering temperature, and sintering aid addition on the phase composition, microstructure, physico-mechanical properties, and leaching characteristics of the novel pyroxene-based ceramics were investigated. The results reveal that the ceramics containing 50 wt% tailings present a single pyroxene phase with uniformly dispersed fine closed pores. At a sintering temperature of 1190 °C, the optimized ceramic achieves a water absorption of 0.33% and a flexural strength of 80.5 MPa. Elevating the sintering temperature facilitates the grain growth of pyroxene crystals and the formation of a liquid phase. The addition of sintering aid effectively lowers the sintering temperature and improves the densification degree of ceramic matrices. In addition, the leaching toxicity of the prepared ceramics is well below the standard regulatory limits. This study provides a novel approach for the high-value recycling of tailings. Full article

The use of phase change materials (PCMs) in cementitious mortars is a promising strategy for passive thermal regulation and thermal energy storage (TES) in buildings, but its practical implementation remains constrained by PCM leakage and its effects on physical and mechanical performance. This study investigates the use of recycled clay brick waste as a dual-function component in eco-efficient mortars, serving as a partial replacement for fine aggregate and as a porous carrier for paraffin-based PCM. The experimental program comprised three stages: selection of an eco-efficient reference mortar, impregnation of recycled ceramic aggregates using thermal and vacuum-assisted procedures, and evaluation of PCM-modified mortars through fresh-state, physical, mechanical, thermophysical, direct thermal exposure, thermoregulation, and infrared thermography tests. Thermal impregnation at 15 wt% PCM provided the most favorable balance between PCM incorporation and stability against surface accumulation and mass loss and was selected for mortar production. Compared with REFeco, PCM incorporation reduced water absorption by approximately 10% and caused compressive and flexural strength losses below 10%. PCM15 exhibited the most favorable thermophysical balance, increasing volumetric specific heat by 14.9% and thermal inertia by 8.5%, while reducing thermal diffusivity by 10.8%. Under direct flame exposure, PCM25 produced the greatest thermal buffering effect, delaying the attainment of 200 °C on the rear face by approximately 4 min and reducing maximum estimated heat flux by approximately 16% relative to REFeco. Overall, recycled clay brick waste demonstrated potential as a PCM carrier for eco-efficient cementitious mortars with thermal energy storage functionality. Full article

Ammonium dinitramide (ADN) is a high-energy green oxidizer with significant potential for use in solid propellants; however, its practical application is restricted by its strong hygroscopicity and low safety. In this study, morphology control and surface coating were simultaneously addressed by preparing ADN/PVA composite particles with different PVA contents by membrane emulsification. At a PVA content of 5%, the ADN/PVA composite microspheres exhibited favorable morphology and a high degree of sphericity, with no phase transition induced and the crystal structure well preserved. DSC results showed that the initial decomposition temperature of ADN/PVA increased by 21.88–26.50 °C compared to that of raw ADN, and the exothermic peak became narrower, indicating that the energy release of ADN was more concentrated and its thermal stability was significantly improved. Meanwhile, the impact sensitivity and friction sensitivity were reduced by 33.33% and 16.67%, respectively, relative to raw ADN, and the moisture absorption rate was reduced by 87.92%. Therefore, the ADN/PVA composite particles prepared by membrane emulsification exhibit excellent thermal stability and anti-hygroscopicity. Full article

Ecologically fragile and economically underdeveloped mountainous regions face the dual challenge of pursuing catch-up development while maintaining ecological security. Although scientific and technological innovation is widely viewed as a key driver of green transition, county-level evidence remains limited on whether, how, and under what conditions innovation improves green development efficiency (GDE) in such constrained settings. Using a balanced panel of 62 mountainous counties in Hebei Province, China, from 2007 to 2022, this study measures GDE with a super-efficiency SBM model, constructs a composite index of technological innovation with the entropy weight method, and estimates dynamic panel models to examine the direct effect, mediating pathway, and heterogeneity of technological innovation. The results are as follows: (1) Technological innovation significantly promotes GDE, but the effect is mainly released through a lagged and cumulative process rather than fully in the contemporaneous period. This finding suggests that innovation dividends in mountainous counties depend on local technology absorption, organizational adjustment, and complementary infrastructure. (2) Mechanism identification confirms that frontier advancement capability, captured by the Technical Change (TC) index derived from the Malmquist–Luenberger framework, serves as a crucial endogenous mediation channel. Innovation systematically lifts the green efficiency ceiling by accelerating the outward shift in the production possibility frontier toward pollution and carbon reduction, yielding a highly significant indirect effect. (3) The innovation–GDE relationship is conditioned by institutional settings and local absorptive capacity. The effect is strongest in counties included in the 2010 cohort of National Key Ecological Function Zones, whereas in low-efficiency counties the innovation effect is positive but weaker and less persistent, so short-term gains do not automatically accumulate into long-term efficiency advantages. These findings provide county-level empirical evidence for designing time-phased and institutionally differentiated green innovation policies in ecologically constrained, underdeveloped regions. Full article

The development of highly efficient catalysts is important for the photothermal catalytic oxidation of volatile organic compounds (VOCs). Herein, MIL-100(Fe) was used as the sacrificial template to prepare MnFeO_x catalysts with different Mn contents through the impregnation–calcination method, and their performance in photothermal catalytic oxidation of toluene was investigated. The results show that the content of Mn significantly affects the crystal phase structure, pore properties, surface chemical state, and optical response of the catalyst. Among them, 30%MnFeO_x exhibits the best photothermal catalytic activity, with T₅₀ and T₉₀ being 211 and 237 °C, respectively, which are significantly lower than those of FeO_x (232 and 260 °C). Characterization results suggested that the introduction of Mn caused the bandgap of FeO_x to decrease from 1.96 to 1.67 eV. Meanwhile, the surface Fe²⁺, adsorbed oxygen (O_ads) species, and oxygen vacancies were increased, enhancing visible light absorption and gaseous oxygen species adsorption and activation, which promoted the photothermal catalytic oxidation of toluene. Additionally, the 30%MnFeO_x catalyst presented good thermal stability and water resistance. Furthermore, during the reaction process, the in situ activation of the catalyst’s surface induced the increase in surface Fe²⁺, Mn^3+, and O_ads species, which enhances the photothermal catalytic activity of the catalyst. Importantly, the in situ DRIFTS results further indicate that toluene is mainly oxidized along the path of toluene → benzyl alcohol → benzoate → maleic anhydride → CO₂ and H₂O. This work provides a theoretical basis for the construction of low-cost, non-precious-metal Mn–Fe-based photothermal catalysts. Full article

The development of sensitive, low–cost, and visually readable dosimeters for low gamma–ray exposures is important for occupational and environmental radiation monitoring and for other low–dose applications. This work investigates a colorimetric and optical thin–film dosimeter based on polyvinyl alcohol (PVA) containing silver nitrate (AgNO₃) and hafnium oxide (HfO₂). The film was fabricated using a solution–casting technique. The dosimetric response was evaluated over an absorbed–dose range of 22.2–65.2 mGy using diffuse reflectance spectroscopy, Kubelka–Munk (K/S) analysis, CIELAB colorimetry, CMYK image–based analysis, and X–ray diffraction (XRD). Irradiation produced a dose–dependent decrease in visible reflectance and a corresponding increase in optical absorption. The K/S response increased with dose, while CIELAB analysis showed a systematic decrease in lightness and an increase in total color difference (${\Delta \mathrm{E}}_{ab}^{\ast }$), reaching approximately 25 at 65.2 mGy. Linear regression of ${\Delta \mathrm{E}}_{ab}^{\ast }$ over 0–65.2 mGy gave y = 0.399x − 1.0029 with R² = 0.9845. CMYK analysis also showed a clear dose response, with the yellow channel (ΔY) exhibiting the largest relative change among the chromatic channels. XRD identified monoclinic HfO₂ as the dominant crystalline filler phase and showed dose–associated changes in peak intensity, peak position, and the relative prominence of the broad PVA–related feature. At the highest XRD dose, several HfO₂ reflections weakened while the broad contribution near 2θ ≈ 19.9–20° became more prominent. These changes are interpreted as dose–dependent structural modification and partial loss of resolved crystalline order rather than definitive evidence of a newly formed crystalline phase. A surface morphology and microstructure analysis was performed on control and γ–ray–irradiated PVA/HfO₂/AgNO₃ nanocomposite films using scanning electron microscopy (SEM–EDX). The morphological transition to fibrous, tree trunk–like structures seen by SEM is well correlated with the dose–dependent change in composition to higher surface Ag content, supporting the idea that radiation–induced Ag nanoparticle nucleation and growth is the primary degradation mechanism in the irradiated films. The combined optical and colorimetric results demonstrate a measurable response of the PVA/HfO₂/AgNO₃ formulation in the investigated low–mGy gamma–ray range. Full article

Porous multi-walled carbon nanotube (MWCNT) films combine strong optical absorption with thermal, Kerr-like, thermo-optical, and magneto-optical responses. However, these effects depend on film structure and may require different design conditions. In this work, a multiphysics model was used to analyze 12 MWCNT film configurations with dependance on thicknesses, porosity, and orientation parameters. The model included optical attenuation, transient heating, nonlinear refraction, thermo-optic modulation, magneto-optical response, and optical phase shift under irradiances of 7–20 MW cm⁻² and magnetic fields up to 1 T. Optical density ranged from approximately 0.4 to 2.8, while transmittance showed negligible variation with irradiance. Thin and porous films produced the highest temperature rises, approximately 4.5 K, and the largest total refractive-index changes. In contrast, thicker films generated larger accumulated phase shifts. The thermo-optic contribution is dominated under nanosecond laser irradiation. As the pulse duration approached the picosecond regime, the lower deposited energy reduced the photothermal response, so the Kerr-like and magneto-optical terms accounted for a larger total refractive-index change. This predictive parametric study identifies architecture- and pulse-dependent trends for future experimental evaluation of multifunctional MWCNT films. Full article

For hydrogen refueling stations, metal hydride compressors offer a safe and efficient alternative to mechanical systems. This work systematically investigates Ti_0.94Zr_0.08Cr_1.0Mn_0.6−xFe_0.4+x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys for primary hydrogen compression targeting 25 MPa. All alloys crystallize as a single C14 Laves phase, with Fe substitution causing negligible lattice changes but leading to linearly increased particle size due to solid-solution strengthening. In the testing temperature range of −80 to −50 °C, the hydrogen storage capacity decreases with increasing Fe, whereas the effective desorption capacity improves. Pressure–composition isotherms exhibit single plateaus with elevated plateau pressures at higher Fe/Mn ratios. In the range of x = 0–0.4, the enthalpy of desorption decreases in magnitude with Fe content. Using Van’t Hoff extrapolations to 30 °C absorption and 80 °C desorption, the compression factor shows a non-monotonic trend, reaching a maximum of 1.99 at x = 0.2. This composition provides nearly a two-fold pressure boost, demonstrating promise for low-grade heat driven hydrogen compression in refueling infrastructure. Full article

Accurate estimation of uniaxial compressive strength (UCS) is essential in geotechnical engineering, but conventional UCS testing is destructive and time-consuming. This study investigates the effects of mild acid exposure and freeze–thaw (F–T) cycling on the relationships between P-wave velocity (Vp) and UCS, density (ρ) and UCS, and Vp and selected physical properties in Apulian dolostone. Thirty-four cylindrical specimens were tested, comprising ten untreated specimens, five specimens in each acid-treatment group (3, 7, and 28 days), five specimens subjected to 10 F–T cycles, and four specimens monitored progressively during F–T cycling. Chemical weathering was simulated by static immersion in sulfuric acid (initial pH ≈ 5) without solution renewal and pH adjustment. Measurements included Vp, density, UCS, apparent porosity, and water absorption, together with thin-section petrography using optical microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), SEM morphology, and X-ray diffraction (XRD) mineralogical analysis (four thin sections per treatment group; one representative specimen per treatment for SEM and XRD). Under the investigated conditions, both weathering processes produced moderate changes in the physical, ultrasonic, and mechanical properties, accompanied by minor microstructural modifications but without detectable mineralogical phase changes. The treatments also modified the empirical relationships between Vp, UCS, and the measured physical properties. These findings indicate that weathering influences the reliability of Vp-based UCS estimation for Apulian dolostone under the investigated conditions and provide new insights into the early-stage deterioration of this material. Full article

To resolve thermodynamic uncertainties in global gas–particle partitioning and persistent organic pollutant transport, this work integrates polycyclic aromatic hydrocarbons (PAHs) into the CHASER V4.0 chemistry–climate model, presenting the first global online simulations of naphthalene (NAP), phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) within this framework to study their fate in the atmosphere. Soot adsorption (K_SA(T)) is coupled with organic matter absorption (K_OA(T)) under an extended Dachs–Eisenreich dual-mode scheme. The coupled model was evaluated at urban, background, and Arctic stations, satisfactorily capturing the broad global spatial gradients (pooled spatial R = 0.78 on a log₁₀ scale; spatial FAC2 = 80% for BaP excluding severe sub-grid hotspots) and seasonal cycles (R = 0.62–0.93). The K_SA(T) scheme rectifies the under-prediction of the particle-bound fraction (φ) in cold high-latitude regions (increasing polar φBaP by up to ~0.6), inherent in the baseline K_OA(T) scheme. Sensitivity tests show that elevated elemental carbon (f_EC) enhances soot adsorption and particle-phase shielding against oxidation, extending the mean lifetime of BaP to 1.72 days (compared to 0.57–0.72 days for lighter congeners) and sustaining transoceanic outflow. Overall, this framework provides an essential tool for assessing transboundary toxicant transport, climate-sensitive health risks, and pollution mitigation policies. Full article

This study investigates the fluorescent and mesomorphic properties of tetrakis(oxadiazolyl)benzenes (TOBEs) and -pyrazines (TOPYs), novel cruciform liquid crystals. The impact of a set of four side chains on optical and mesomorphic properties is reported. TOBE absorbs in the UV range (~360 nm), while substituting the central benzene ring by pyrazine (TOPY) shifts the absorption maximum to 396 nm but lowers the fluorescence quantum yield (TOBE: 72%; TOPY: 21%; in toluene). Fluorescence in the green-to-orange range is influenced by solvent polarity. Mesophase analysis shows quite narrow phases (~20 K) for TOBE. As the pyrazine core lowers the melting point and elevates the clearing temperature, huge mesophase ranges (~80–90 K) are detected for TOPY. Side chain variations further influence material properties: TOBE with linear alkyl chains exhibits multiple crystal–crystal transitions, while branching enhances mesophase stability and alters fluorescence characteristics. The Huisgen reaction provides a cost-effective synthetic route for these fluorescent mesogens, offering high yields and efficiency. Full article

Organic–inorganic hybrid perovskites (OHPs) deliver certified single-junction power conversion efficiencies (PCEs) of up to 27.3% and National Laboratory of the Rockies (NLR)-certified perovskite–silicon tandem values of 34.85%, yet a substantial gap with the Shockley–Queisser (S–Q) limit persists. Grain-boundary (GB) defects are one principal contributor to this gap, driving non-radiative recombination, ion migration, and degradation alongside bulk, interfacial, contact-related, phase-related, and environmental loss channels. Rational passivation demands a non-contact tool capable of identifying and quantifying specific defect species in device-relevant thin films, a capability that conventional probes deliver only in part. This overview assesses the extent to which terahertz time-domain spectroscopy (THz-TDS, 0.2–2.5 THz) fulfills this role. Across five OHP compositions—MAPbI₃, MAPbBr₃, FAPbI₃, and FAPb(Br,I)₃ fabricated by sequential vacuum evaporation (SVE), together with solution-processed γ-CsPbI₃—the THz spectral window captures both intrinsic phonon modes and GB-localized molecular defect vibrations, enabling species-resolved characterization at room temperature. Notably, the oscillator strength of the SVE-specific 1.58 THz absorption in MAPbI₃ scales linearly with XPS-quantified CH₃NH₂ defect concentration, establishing a calibrated, contact-free proxy for defect concentration rather than an absolute defect count; the observable is the defect-induced perturbation of the Pb–X lattice, not the defect population itself. Building on these findings, we propose a three-pillar framework for THz-guided defect engineering: (I) quantitative defect measurement via oscillator-strength analysis, (II) material-specific fingerprint identification from a systematically constructed THz library, and (III) fingerprint-guided defect elimination with real-time feedback—together defining a closed-loop quality-control cycle that connects spectroscopic diagnosis to passivation strategy and, ultimately, to enhanced solar cell efficiency. Throughout, we distinguish capabilities demonstrated to date from extensions that remain proposals, and we define the measurement requirements needed before the framework can be transferred to inline manufacturing control. Full article

Asphalt pavements suffer from progressive deterioration during service life due to aging, while conventional polymer modifiers raise environmental concerns regarding recyclability and volatile organic compound emissions. Functionalized-biochar derived from renewable biomass offers a sustainable alternative through its tunable surface chemistry and porous structure. This study develops and evaluates a nitrogen-rich, surface-functionalized biochar as a multifunctional asphalt binder modifier and elucidates the synergistic roles of inherent nitrogen and post-synthetic functionalization in governing binder performance. To this end, soybean powder was pyrolyzed to prepare the biochar precursor, which was subsequently characterized to determine its suitable pyrolysis temperature and surface properties. These analyses identified 300 °C as the preferable pyrolysis temperature within the tested range of 200–500 °C, maximizing biochar yield and achieving favorable surface physicochemical properties including the iodine adsorption value, oil absorption value, surface functional groups and pore morphology. To improve surface functionality, the biochar underwent a two-step modification: nitric acid oxidation followed by hydroxymethylation, hereinafter referred to as functionalized-biochar. The influence of functionalized-biochar content on asphalt binder performance was evaluated across dosages of 10–20 wt%, and 15 wt% was identified as the recommended content. Asphalt binder modified with 15 wt% functionalized-biochar exhibited improved high-temperature performance, as evidenced by enhanced rutting resistance factor G*/sin δ values obtained from dynamic shear rheometer testing. Aging resistance also improved, reflected in a lower complex modulus aging index and a higher phase angle aging index. At 15 wt% dosage, the softening point increased by 6 °C, and ductility rose by 10.6 cm relative to the base asphalt (1.9 cm), corresponding to a 557.9% improvement. Penetration declined by 17%, while the complex modulus aging index decreased from 3.44 to 1.68. Notably, the experimental program in this study was limited to binder-scale characterization. Full article